Quick fixes for the problems players run into most. For a message the game shows you, see Error messages. Still stuck? Ask in our Discord.
The Somtum Patcher adds Relax and Autopilot scores, the live pp counter and its own options to osu!(stable) by changing the game while it runs. Each osu! update can move the code it changes, so on some builds a feature doesn't switch on. You might see no Relax/Autopilot scores, no pp counter, or a message that a feature has been disabled for your osu! build.
Try the cuttingedge release stream. In osu!, open Options → General → Updates, set Release stream to Cutting Edge, let osu! update, close it, and start it again from the Somtum Patcher or the Somtum Launcher. If it still doesn't work, tell us on Discord which osu! version you're on (it's shown under Options → General → Updates) and which feature is missing.
Some antiviruses (Windows Defender among them) flag tools that change a running game, so they sometimes block the Somtum Patcher or our anti-cheat, pkms.dll, by mistake. Download it again from the download page and add an exception for its folder. Without the anti-cheat your scores aren't submitted.
They aren't allowed: they put their own opengl32.dll, d3d9.dll or dxgi.dll next to osu!.exe, the way some cheats load. Delete that file from your osu! folder (see Playing with the Somtum Patcher).
A first start under Wine can be slow. If you see "osu! did not finish starting within 10 seconds", just start it again: the second start is usually quick. See the error message.
TumThai keeps its own files, apart from osu!lazer's. See bringing your osu!lazer beatmaps and replays.
Usually your TumThai is out of date: an installed TumThai updates itself, or download it again from the download page. The message says why underneath; see Why didn't my score submit?.
Old builds need .NET Framework 3.5 (a few 2015 builds need .NET Framework 4). On Windows 10 and 11, turn it on in Control Panel → Programs → Turn Windows features on or off → .NET Framework 3.5. Keep pkms.dll next to osu!.exe, or your scores aren't submitted.
Confirm the device on the verification page (sign in to this website first), then log in again. See the error message.