When you load an NTSC or JAP game, then when the screen stays black, do you still hear the sound from the game? Try a game like Goldeneye, which has sound straight from almost the moment it boots. If you have a black screen but sound, then it means that your TV probably doesn't support NTSC or JAP signals. Most modern TVs do support NTC/JAP, but not all. There might be an option on your TV to support this mode, but I've never seen one.
If there is no sound either, then presumably the game rom is corrupt. Try downloading the game roms from a different source, and try those newer roms.
I am a PAL user (I live in England), and my (PAL) TV had difficulty showing some NTSC/JAP games, so I eventually bought a new TV. Because of the Covid lockdown, I couldn't go in to a shop with my N64 and test any potential new TVs, so I had to take a chance and buy a TV online, because for some reason, no TV manufacturer seems to list what old consoles will work with their TVs. And my new TV does a *terrible* job of displaying N64 games. It does show all three regions, no problem there, but all three regions look terrible, so I've ended up buying a RetroTINK 2X Pro and it makes my TV display N64 games much more clearly. It's still not ideal, sadly, but it's the best I could do for this TV, I think, other than getting an UltraHDMI (which gives a superb picture on any TV that has a HDMI input), but they aren't in production anymore (and scalpers are selling them for ridiculous profits) and weren't easy to find anyway. The bloke who made the UltraHDMI is apparently now working on a new version, so perhaps we'll be able to get them cheaply and easily in the future.