After lowering the feed teeth I am unable to raise them manually with the dial. They do raise with a mechanical "clank" as I begin to sew. The feed teeth are on the extreme right off the slot openings. Shouldn't they not be centered in the slots?

go google and type in --user manual for singer sewing machine model 4423---and download the pdf version
you could always talk to the singer shop for advice or join a sewing club to get expert tips to get the best out of your machine

Some machines need the dial put in a certain position, try moving it about as you try to move the feed dogs. The presser foot must always be up.

A set of feed dogs typically resembles two or three short, thin metal bars, crosscut with diagonal teeth, which move back and forth in slots in a sewing machine's needle plate. Their purpose is to pull ("feed") the fabric through themachine, in discrete steps, in-between stitches.


Feed dogs - Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Feed_dogs Wikipedia

Look at the presser foot and imagine they are at the center of a clock. Now look at 4:00. There is a horizontal wheel (dial) on the free arm that needs turning.

The feed teeth are lowered when you turn the dial on the front of the free arm to the left . Turn the dial to the right if you wish to raise the feed teeth. The feed teeth will raise as you begin to sew.

Look at #12 on page 2 here: http://new.husqvarnaviking.com/sitefiles/clientsite/57/57c874e2-c4de-4acc-a703-3d47b01f941b.pdf

The Sapphire will not raise the feed untill it makes one or two stitches after it has been lowered. Good luck

Unable to locate a manual for your machine. You might try contacting a Toyota dealer or Toyota support. You may try totally rethreading from the beginning again. Make sure everything is correctly set before beginning to sew, ie presser foot lowered, stitch length & stitch width are set, the bobbin winder is deactivated, feed dogs are in raised position...

Here is a link to page 22 of the manual. It shows you where to flip the lever to raise the feed dogs. If your feed dogs are not grabbing fabric your feed dogs are lowered.

https://www.manualslib.com/manual/1050311/Singer-2638.html?page=23#manual

HOW TO FIX YOUR FEEDER TEETH (DOG TEETH) ON EMERALD 116/118/120 IF THEY STOP WORKING....

So this is just a temporary solution to this problem... after reading through the user's guide (which really needs to be updated to have more troubleshooting suggestions), and basically taking apart various parts of the machine, I found a temporary solution.

1. Unscrew the Face Place (where the needle is attached to. #9 in User Guide Overview) There is only one screw on the side right underneath the Pressure Foot Pressure Dial (#8 in User Guide Overview). Taking off the Face Place gives you room to use a screwdriver for step 2...

2. Unscrew the Needle Plate (#12 in User Guide Overview), and take out the Bobbin holder (black). Slide the lever for the Feed Teeth to the raised position, and with your forefinger pop up the Feed Teeth (underneath the needle) to the raised position. You will here a click... and you are set to go. Reassembly your machine and get back to sewing!

If you do not have a button or lever near the teeth under the plate then you should have a raised plate

If the machine has been taken apart it may have been reassembled improperly so that the dial on front of freearm is interfering.
Also, try removing the needle plate. If the teeth touch the side of the plate they may not drop properly.