I have bad news and more bad news.
The transmission of your unit has gone bad. And the transmission is no longer available at two parts sites that I looked at.
There is a picture tutorial on Flikker that if you wish you can go and see what is going to be involved repairing your unit. There are also two special tools you will need to remove a couple nuts.
I'm sorry that it is not better news. From what I can determine without seeing your unit personally it is better if you retire it and look for another one.
I highly recommend you avoid the GE models as there is very little information available for them. The other thing I recommend is you avoid anything that is digital. they are expensive to have repaired. The good old push the timer knob to start are the best and most reliable units still to this day.
I am sure that this is not what you wanted to hear, but it is the only honest answer there is. I, unfortunately, have no control over some of the answers that I must give.
I would appreciate it if you would honor the time I have put into researching, and answering your question by clicking on the accept button.
Best regards; The Home Smithy
Once you have clicked on the accept button, please be sure to leave positive feed back for me.