Flywheel is tight

Is the safety lock engaged ? To prevent you from accidentally stabbing yourself while changing the bob in?

E7 means
The start/stop button, reverse/reinforcement stitch button
or the thread cutter button was pressed while no thread
cassette was installed. If the start/stop button is pressed before the sewing machine is correctly set up or if an operation is performed
incorrectly, an error message appears in the stitch indicator. Follow the instructions that appear.
If you press (Stitch selection key) or do the operation correctly while the error message is displayed, the
message disappears

Have you cleaned and oiled it lately? All that fine dust can jam things up tight.

I would call a sewing machine repair shop and ask how much it would cost to have the machine serviced and fixed and then you can decide wether or not it would be worth having the machine fixed or looking for a newer machine...

what the name & model number of the machine?

This is not what you want to hear but... recheck the threading yet again. This time totally unthread it and start again. Look at the spool that holds the thread and where the thread is coming off of the spool itself. Look to see if the little notch you take the thread out of when you first open a new spool is catching the thread as it turns on the spool. If there's a possibility that is happening make sure that end of the spool is at the top. Sometimes the thread will get catch and therefore refuse to move when it is on the bottom side of the spool.

Also check to make sure the thread isn't wrapped around any of the guides and once again check to see that it is threaded correctly.

If it isn't just the thread breaking but the machine itself seeming to lock up and not move then you need to take it in for servicing.

The safety device will activate if the machine has a bind or is unable to run at correct speed. If you turn the handwheel is it tight/hard to turn? if it is than thats it. Now what is binding the machine has to be diagnosed.

H there,

Initially, Turn power off and wait about 20 minutes. Safety device will reset, and machine will be ready to operate.

Let me know

Try removing the screws that hold the needle plate on and take it off, remove the bobbin case and check for loose thread in the bobbin area. Sometimes machines lock up when a small piece of thread gets under the bobbin case, this is called being "thread locked". Hope this helps. I'll see what I can find out about the "88" error message.

My Kenmore 19606 sometimes gives me that error message when I am holding my fabric taut (on either side of the foot) and I accidentally exert pressure on the needle (that is, tug forward or back on the fabric pulling at the needle)... I found that when it gives me that message and then pauses for a while, cranking a few stitches by hand seems to "recalibrate" it if you will, and bring it back to normal operation sooner... If you're not a tugger like me... =op =o) Maybe the needle needs replaced? It might be slightly bent, or not screwed in properly..?? Don't know if that helps! Good luck!