Start stop button disable, how do I get this to work

Here are the steps to sew a buttonhole on the Janome New Home My Excel 18W/MW3018 sewing machine:

1. Attach the buttonhole foot to the machine.
2. Place the button in the back of the buttonhole foot and adjust the foot so that the button fits snugly.
3. Select the buttonhole stitch on the machine. It may be a buttonhole symbol or a number corresponding to the buttonhole stitch.
4. Set the stitch length to the desired length for the buttonhole. The machine may have preset lengths or you can adjust it manually.
5. Place the fabric under the foot and lower the foot.
6. Sew the first side of the buttonhole. Stop the machine when it reaches the end of the buttonhole.
7. Sew the second side of the buttonhole, stopping at the end.
8. Use a seam ripper or scissors to open the buttonhole carefully.
9. Remove the fabric from the machine and trim any loose threads.

Make sure to practice on a scrap piece of fabric before sewing the buttonhole on your project.

I don't know that machine, but generally on older machines, you put a buttonhole foot on the machine, set one of the buttons in the back-end of the slot so that it adjusts the size needed automatically. Then you set the machine stitch setting on 1 and set the width to make a satin stitch (a close zig-zag) down one side of buttonhole. You sew until the buttonhole foot makes the button hit near the foot; it will stop you, basically. Then you change stitch dial to 2 to make the bottom of the buttonhole, then 3 to make the other side, then 4 to make the top side. Then you remove the fabric and cut open the buttonhole (I use FrayCheck fist) Try some buttonholes on scrap fabric first, you will figure it out by trial and error.
If your machine is newer, they automatically can sew a buttonhole, but each one does it differently, Sorry.

sure, put on the buttonhole foot after putting a button into it and using the screw knob to set the length you want.
Turn stitch length knob and stitch width knobs to zero, (always set them to zero first to avoid wear on the stitch selection mechanisim) then turn the left stitch selector knob to the blue button hole symbol. Now turn middle knob stitch width, to the blue buttonhole symbol. Now turn right knob stitch length to blue 1, sew down the first side of your buttonhole until foot slide in the buttonhole foot reaches end stop. raise needle and turn stitch length to blue 2, and sew three bar tacks across buttonhole. Again, raise needle and then turn stitch length to blue 3 and sew back down otherside of buttonhole until you reach the end stop. Needle up, turn length know to blue 4 and sew three bartacks to end. there is a last blue symbol dot on stitch length knob, this will sew a stitch in place to tie off the ends. Raise pressure foot, remove your work and draw top threads to underside with a needle, and tie off or use a dot of fray stop. Done! if you don't have a manual you could email me and I'll send you a copy of mine, tallygirl98 at yahoo dot com.

In order to use the start/stop button the foot pedal must be unplugged.

you should a buttonhole button that must be pushed on the machine
either before you pull the buttonhole lever down or after to let the
sewing machine know what function to use, my sewing machine
won't let me make a buttonhole unless I push the buttonhole button
or yes, like you said the buttonhole foot could be damaged.

Brother Computer Codes

• E1: Make sure the presser foot is lowered before sewing.
  E2: You chose a stitch other than a buttonhole stitch or a bar tack stitch and you tried to sew with the buttonhole lever in the lowered position. Raise the buttonhole lever.
  E3: If you selected the buttonhole or tack bar stitch and start to sew with the buttonhole lever raised, you will get the E3 code. Lower the buttonhole lever.
  E4: You hit the reverse button while the bobbin winder shaft was moved over to the right. Move the bobbin winder shaft to the left.
  E5: On automatic sewing machines, the start/stop button was pressed while the foot controller was plugged in. Unplug the foot controller if you are using the automatic function.
  E6: This code tells you that the motor locked up because the thread is tangled. Untangle the thread, make sure the machine is threaded properly and that the proper tension is set before continuing.
  

I've been looking too and I found here http://sewing.patternreview.com/cgi-bin/sewingclasses/board.pl?t=18328that you need to put the bar behind the needle threader down. I think they call it a button hole stop? I don't know, but it worked. I didn't even know it existed. But it solved my problem. On my Kenmore it looks like a black lever and you pull it down. It tells the button-holer that you are at the end of the hole and it needs to backup. nifty, kind of.

Move the width bar to between 4 and 6, the higher number makes a wider buttonhole. Move the length bar to the middle or right of the buttonhole icon. Set the selector dial on #1, snap on the buttonhole foot with a button snugged up in the back slot. Pull down the button stop lever behind the needle threader and make sure it is lower than the edge of the buttonhole foot, and behind the little tab on the left side of the buttonhole foot. Position the needle over where you want the bottom of the buttonhole to be. It will bartack, sew backwards, bar tack and sew forward based on the size of your button. When it is finished it will stop sewing. Turn the stitch selector dial to #2 to reset, then back to #1 to sew the next buttonhole. Practice on scraps until you are happy with the stitch length and width.

Put on the C foot. Select the buttonhole stitch. The machine will start sewing in the bottom left corner of the the buttonhole. Sew the length that you need, press and release the reverse button and sew the right side of the buttonhole. When you get back to the bottom, press and release the reverse button again and the buttonhole will be finished and the thread will tie off and the machine will stop. If the buttonhole is what you want, press and release the Stop button and the machine will repeat this buttonhole as many times as you need until the machine is turned off or the Stop is pressed again. When repeating, you need not press the reverse. Just press down on the foot control and continue until the machine stops by itself.
If you don't like the first one, just sew another one using the reverse button to set the ends.

Here ya go! For 1 Step Automatic Buttonholes: 1. Place button into the buttonhole attachment. 2. Push slider to hold button securely in the slot. The button goes to the back! 3. Put button foot onto needle bar--just attach it securely. 4. Place needle thread and bobbin thread UNDER buttonhole attachment and let 4"-5" of thread trail behind it. 5. There's a lever called a Button Stop to the left of the needle bar. Give it a gentle tug and pull it down. Pull forward. Hear a click? Now the machine knows what length to STOP sewing! 6. Put foot on pedal and machine will sew barrack closest to you first. It will continue all around until it makes complete rotation of each side. 7. You must do these steps for each of your buttonholes! IMPORTANT: Make sure you set your dial for making buttonhole pattern because that "tells" machine to zig zag, and use appropriate size needle for the particular weight of your fabric. A new needle before you begin is recommended. Turn screw on needlebar to loosen screw. Hold it so it does not slip down into the feed dog area! New needle is inserted flat shank toward back of needlebar as far as it will go. Tighten screw. Did this help? Hope so!
Jimmy