2016 5.3 chevy silverado 1500.

I bought this 2016 5.3liter 8 cylinder chevy silverado 1500 with 60k miles and the first thing i did was buy an afm/dfm disable device that plugs into the reader beneath the steering wheel. Kept it in 8 cylindwr mode and never had an issue. I took it in to a gerber collision shop to have a dent repaired through insurance at 101k. for reasons beyond what i can fathom they decided they needed to unplug my device (idk why they would need to pkug a reader in to fix a dent ( also no lights were on on the dash no check engine no NOTHING)) i got the truck back and driving home i noticed it was in 4 cylinder mode. So i plugged my device back in and the lights on the device wouldnt come on. Figured maybe i just had to have the truck off when i plugged it in. So the next morning i go and start my truck and it shuts off after a few seconds and starts flashing service 4wd, service trailer brake, service power steering, service EVERYTHING. It wouldnt start, just click until i unplugged the device. And if i plug it in when its running it drops the tach to 0 and start fladhing every service message possible and my check engine light is on now. And ideas why it was fine for a year and now just completely fucked?

I bought this 2016 5.3liter 8 cylinder chevy silverado 1500 with 60k miles and the first thing i did was buy an afm/dfm disable device that plugs into the reader beneath the steering wheel. Kept it in 8 cylindwr mode and never had an issue. I took it in to a gerber collision shop to have a dent repaired through insurance at 101k. for reasons beyond what i can fathom they decided they needed to unplug my device (idk why they would need to pkug a reader in to fix a dent ( also no lights were on on the dash no check engine no NOTHING)) i got the truck back and driving home i noticed it was in 4 cylinder mode. So i plugged my device back in and the lights on the device wouldnt come on. Figured maybe i just had to have the truck off when i plugged it in. So the next morning i go and start my truck and it shuts off after a few seconds and starts flashing service 4wd, service trailer brake, service power steering, service EVERYTHING. It wouldnt start, just click until i unplugged the device. And if i plug it in when its running it drops the tach to 0 and start fladhing every service message possible and my check engine light is on now. And ideas why it was fine for a year and now just completely fucked?