OBD scanner not connecting/no reset
2004 Duramax 2500. I was unable to register my car because I had a P380 code. I found and fixed the bad glow plug and checked that the circuit was good. The scanner i borrowed from Autozone still reads the code (so I know the port is good) but doesn't do resets, and the 2 scanners I've bought won't connect to the ECM for some reason. I've tried several reset tricks I've seen on YT but to no avail, the code remains. AAMCO won't do resets unless you let them work on your vehicle but since I've already don't the repair I really don't want to spend money for them to redo my troubleshooting.
Any advice aside from spending hundreds on a more advanced scanner?