Slide not working is almost always the 30 amp fuse at the battery.
My fiver came with single blow fuses installed.
My VERY first mod was replacing them (I have two) with 30 amp circuit breakers.
Look in the immediate vacinity of your battery as the fuse MUST be located within 18 inches. I am assuming the fuses you checked were in the converter panel not at the battery itself.
Lou, Laura, & Freya the wonder dog
2008 GMC Sierra 3000HD Crewcab SB Allison Duramax
2019 Flagstaff 8529FLS - Pullrite 3300
HAM CALLSIGN - KC3FFW