Well, if the N64 isn’t displaying any image on the TV screen, you should try another TV cable, only if (I know that it’s a dumb assumption but, nvm) you’ve connected the RCA connectors wrongly, each RCA port from the TV has a color which has to be matched with the respective connector.
If the AV cable replacement won’t help, you could try reseating the cartridge, or/and blow into it’s connector pins, maybe the problem is in cartridge’s old pins.
If this won’t help too, then the problem can be in the console itself.
P.S. Idk what HDMI adapters you’ve tried, but you'd better buy decent converters like same OSSC, because not every converter will output a decent quality on a modern TV.