Try to repair osu!
In the wise words of Kao
Here are steps you can do to repair osu!
Method 1: Launch Repair Dialog- Hold down the Shift key on your keyboard.
- While holding Shift, double click the osu! icon on your desktop.
- Continue holding Shift until you see the recovery dialog prompt.
- From there, click on the "Repair osu!" option
Method 2: ShortcutIf you have the "repair osu!" Shortcut, opening that also works.
Method 3: Config ShortcutIf you don't have the "repair osu!" Shortcut, you can create one instead.
- Right click osu!.exe > Create a shortcut
- Open properties of the shortcut
- Select then Alt + Enter or
- Right click > Properties
- Set Target to ...\osu!.exe -config
- Press OK then open the shortcut
Method 4: Text documentYou can also force the updater to run by creating a new text document in your osu! folder called "help". Right-click in an empty space in your osu! folder, and choose New > Text Document.
Name it help and then run osu! to start the updater in forced maintenance mode.