I’ve seen this a lot and honestly it’s usually a mix of server instability + client‑side network issues. Marvel Rivals does a bunch of checks in the background (matchmaking, sync, rank updates), and if anything hiccups it tends to throw a generic error. First thing I’d check is whether servers are stable that day threads have been blowing up whenever there’s a new patch drop or a big event live.
Also make sure you’re not playing during peak maintenance windows those aren’t always announced clearly.