Discord opens, announces an update, fails, and retries forever. The loop lives in the updater and its local cache, not in your account. Typical causes: a half-downloaded update that keeps failing its checks, leftover Discord processes holding files, antivirus blocking the updater's writes, or a corrupted local app data folder. The reliable cure is a clean removal of the app data folders followed by a fresh install.
Win+R, run %appdata%, and delete the discord folder's Cache and the Update related files; simpler and safer for most people is the full clean reinstall in step 4.%appdata%\discord and %localappdata%\Discord folders, restart the PC, and install from Discord's official site. Your account, friends, and servers live on Discord's side, nothing social is lost.A normal uninstall leaves the app data folders behind on purpose, so settings survive. The update loop lives exactly in that leftover data, so reinstalling over it re-imports the fault. Deleting those two folders is what makes the reinstall 'clean,' and it is the step most quick guides skip. You will need to sign in again and redo settings like keybinds and overlay choices, a fair trade for an app that opens.
Will I lose my servers and messages with a clean reinstall? No. Everything social is stored on Discord's servers. You lose only local settings and will sign in again, two-factor code handy.
It updates fine on another PC. What is different about mine? Usually the security software or the state of those app data folders. The clean reinstall plus an antivirus whitelist addresses both, and if it still loops, testing a different Windows user profile separates profile corruption from app corruption.