when you replaced Main Relay are you talking about the one under the Hood?
those Relays can go bad so i would replace all the Relays, they are Black and Grey usually
my DRL Relay will kill all my Lights but it is in there, and i believe previous owner disabled it even with DRL Relay in place under Hood
sounds like it could be electrical
if you suspect maybe previous owner tinkered with it, signs of wiring, decals everywhere, etc...i found it easier to swap out the entire thing.
i.e. start with the Under Hood relays, 5 or 6 i believe, then maybe swap the whole under Hood unit first