Can not get 2020 iMac into DFU mode

i have 2020 iMac. Out of no where it started saying computer is disabled and shows firmware lock. I logged into find my app online. It shows a lock next to my imac. But says pending. i cant get to do nothing. I cant get it into DFU mode. Press power button then plug cable in and wait for 3 sec method. Tried 4 different usb c cables and two different mac computers no luck. Any idea what i can do? I dont have receipt. Apple says cant help without receipt even though i have login to find my account and it shows in there.