What is the voltage at the battery terminals when you are plugged into 50 amp?
If less than 13 volts you have either an open circuit breaker (right before the red wire gets to the battery, corroded wire connection somewhere from the converter to the battery, or a bad converter.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW