Error 0x8004de40 appears when OneDrive starts and cannot complete sign-in, often with wording that there was a problem connecting to OneDrive. Microsoft documents two dominant causes: the account password changed and the stored credential no longer matches, and the PC's TLS 1.2 setting being off, which modern Microsoft sign-in endpoints require. Network filtering that blocks the sign-in endpoints produces the same code.
%localappdata%\Microsoft\OneDrive\onedrive.exe /reset. The icon disappears for a minute or two and returns; files are not deleted, and sync state is rebuilt.On managed work machines, 0x8004de40 that survives all of the above is commonly a proxy or conditional-access block: the sign-in reaches Microsoft but the organization's policy rejects this device. That is an IT-department fix, and the web sign-in test in step 2 helps show it, since the web sign-in typically reports the policy refusal in plain words.
Does resetting OneDrive delete my files? No. The /reset command rebuilds the app's local state and re-checks the library against the cloud. Files in the OneDrive folder and in the cloud are left in place.
Why did 0x8004de40 start right after I changed my password? Because the stored credential no longer matches the account. OneDrive keeps trying the old password, sign-in fails, and the failure surfaces as this connection-style code rather than a clear password message.