Excel password

If the workbook is stored on a network drive, OneDrive, SharePoint, or another cloud location, Excel may be asking you to sign in to Microsoft 365 rather than requesting a file password. This can happen after a password change, Windows update, expired sign-in token, or if Office has lost your saved credentials. Signing back into your Microsoft account in Office often resolves this type of prompt.

If the prompt specifically says that a password is required to open the workbook, then the file itself may have been password-protected. This could occur if someone else created or modified the workbook, or if the file was restored from a backup or copied from another location where a password had already been applied. Excel cannot recover or bypass a genuine workbook password.

Another possibility is that the workbook is opening in Protected View or has information rights management (IRM) or sensitivity labels applied by your organization. In a business environment, security policies can require authentication before certain files can be opened, even if they did not previously.

It is also worth considering whether the file you are opening is actually the original workbook. If there are multiple copies with similar names, you may have inadvertently opened a different version that is password protected.

If this behavior has only started recently, try opening a different Excel workbook. If only one file requests a password, the issue is likely with that workbook. If every workbook prompts for credentials, the problem is more likely related to your Microsoft 365 sign-in, Windows credentials, or your organization's security policies.

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hth

Marcin