Top 5 Reasons Why You Don't See Anyone in SHAR Multiplayer

You don't have the correct mods as someone else

Maybe you do see at least one player in the list I linked but still don't see them in-game. You may not be using the correct mods. Just look at the mod(s) the players are using and drag the corresponding mods to your launcher's executable. You'll find the other players unless you made another common mistake that's so similar that it also deserves to be numbered 5.

You don't have the correct mutators as someone else

You have the same mods as the other players but you're still somehow separated from them. In your launcher's Mutators tab, check to see if they match the ones shown in the player list. If they don't match, you'll be put in a different room.
Bomb icon = Allow Explosions
Police icon = Cops and Robbers
MirrorMode as the mod used = Mirror Mode
NoCheats2 as the mod used = No Cheats

You're using the general Mod Launcher instead of the SHARMP launcher

Lucas' Simpsons Hit & Run Mod Launcher is different from the Multiplayer launcher. The former does not support multiplayer. Maybe in the future, the multiplayer launcher will become obsolete. For now, it gets the job done.

You messed with the textboxes in the SHARMP launcher's Server tab

Those textboxes in the SHARMP launcher's Server tab should remain untouched as they don't mean anything. No one has a clue why it's there if it's never going to be used, but they should be left alone. Those textboxes are doing something. They're just currently useless. There's only one server that SHARMP can connect to, and the launcher's settings already default to that server.

No one actually plays SHAR Multiplayer

There just isn't anyone playing Multiplayer. We're a small modding community, so randomly finding a session with 4+ players is very rare. Unless you're lucky enough to find someone hosting an event in SHARMP, you won't find yourself playing with many people. None of the long-time members here play SHARMP. There's another good reason why it's always so empty. See #1.

SHAR Multiplayer sucks

Even the Donut Team staff agree with this one. Despite how many people join the Discord to request others to join them, there's a reason why they don't return: SHAR Multiplayer is boring. There's nothing to do in it besides ram each other, circle around the maps, and spam the explosion key. No missions, no destructible vehicles, no CPU players, and no convenient way to change characters. Players will soon realize SHARMP's major flaws when trying it for the first time and never come back to it the next day.

Before SHARMP was conceived, there was an extreme demand for it. Lucas went ahead to whip up a bare bones implementation of SHARMP. After Donut Team released a video demonstrating SHARMP in action, they were pressured to death by thousands of requests to release the hack. All that pressure led to the team publicly releasing the same bare bones version of SHARMP and look how it turned out. The team calls this an "official leak" since it wasn't intended to be released to the public. Blame the community's outcry for the lack of features. You won't see Donut Team improve SHARMP any time soon. After that disaster, they learned their lesson of not releasing any more half-assed stuff like that. Or at least they're trying to anyway.

A popular gamer is not present

Is your favorite gamer in SHARMP right now recording footage for a video? Didn't think so. Good luck finding anyone hosting SHARMP events because hardly anyone does them. Even then, they turn out badly at the end of the day. That's why even Nightbane doesn't do them often, and he currently holds the record for most events hosted (4). If you came here because of some YouTube videos showcasing this proof-of-concept Multiplayer hack, you were pretty much misled. Those sessions were only so populated because someone well-known started an event.

We're not a multiplayer community

Basically re-stating what I said in #2. We're solely a modding community, not a multiplayer community. Most of us came here for SHAR mods. No one in the Discord server has SHARMP in their mind these days. We only look forward to more mods and stuff. I can't speak for everyone, but the constant requests to join sessions have progressively gotten more irritating.