8K Generac air
Installed Nov. 2012
Twice yearly maintenance

The original thread describing my problem is missing, but I promised I would come back with the answer when fixed.

To recap: unit underwent Fall maintenance with passing checks except tech oddly reported it subsequently wouldn't start for him. In following few weeks it worked for exercises with no problem only to suddenly go dead with no lights or display. I tried a bit of  troubleshooting without opening up the transfer switch box (too chicken) but no luck.

Had to wait three weeks for repair appt and after much back and forth from unit to the transfer switch, tech said that the fuses tested OK however he discovered one of them in the transfer box was loose in its bracket. He replaced the battery and it started up. It came on today for its exercise so I'm hoping that was all it was.

He showed me the fuse that was the one causing the problem and said I could push on the center of it if I encountered the situation again. I'm a senior woman who is relatively capable at home repair but am justifiably nervous when it comes to electrical items. Outlets and light switches are within my grasp, but not comfortable in circuit boxes so I am not sure whether his advice is safe. Opinion?

Thanks for all your comments in the earlier thread. You guys really know your stuff. :-)
A fuse should not be getting loose.  If the fuse holder is incapable of holding the fuse securely the fuse holder should have been replaced.

Do not push on the center of the fuse with your bare finger.  Use a piece of insulating material such as rubber or plastic or dry wood.
Turn all of the power off first, the power company feed and the generator.
I always turn off all power, and then use these for dealing with fuses: https://www.amazon.com/gp/product/B000GAS3Q2/ref=od_aui_detailpages00?ie=UTF8&psc=1

They might not be of the grade that the pros here use, but my fingers are not going anywhere near the magic.
C'mon guys, It's only 120v to ground, it just tickles a little. 👻
You all confirm my initial skepticism about touching anything in that box. That fuse puller looks interesting but I think I'll just call them back if I encounter the same problem and make them fix the fuse holder.

Thanks again. :-)