Outlook is no longer accessing my Gmail account.

Create a new Outlook Data File, make it the default data location, restart Outlook, and then remove and re-add Gmail; Outlook blocks removal because Gmail is currently the profile’s only account.

Replace the only Gmail account

1. Preserve any Outlook-only information first.
   • Gmail configured through IMAP normally uses an .ost file that synchronizes with the server, so that file itself does not require backup.
   • If Outlook contains local-only folders, contacts, or calendar items, export them first through File > Open & Export > Import/Export > Export to a file > Outlook Data File (.pst).
2. Create another data location.
   • In Outlook, select New Items > More Items > Outlook Data File.
   • Enter a file name and select OK. Outlook normally saves the .pst under Documents\Outlook Files.^1^
3. Make that new file the default.
   • Select File > Account Settings > Account Settings.
   • Open the Data Files tab.
   • Select the new .pst, choose Set as Default, and accept the prompt.
   • Close and restart Outlook so the change takes effect.
4. Remove Gmail.
   • Return to File > Account Settings > Account Settings > Email.
   • Select Gmail, choose Remove, and confirm.
   The warning you encountered is expected when attempting to remove the last account before creating another data location.^2^
5. Add Gmail again.
   • Select File > Add Account.
   • Enter the Gmail address and select Connect.
   • Complete Google’s browser sign-in.
   • On the Google permissions page, allow Microsoft apps & services to read, compose, send, and delete Gmail messages.
   • Select Done, then test both sending and receiving.

Cleaner fallback: create a replacement profile

If Outlook still refuses to release the account, leave the existing profile intact initially and create a new one:

1. Close Outlook.
2. In Windows Search, enter outlook.exe /manageprofiles and press Enter.
3. Select Show Profiles > Add.
4. Name the profile and add the Gmail account.
5. Set Always use this profile to the new profile, or choose the option that prompts for a profile.
6. Start Outlook and verify that Gmail sends and receives correctly.
7. Only after confirming that required data is available, return to Show Profiles, select the old profile, and choose Remove.

Deleting a profile removes its configured accounts and offline data, but associated .pst files remain on the computer.^3^

If Gmail still cannot connect

Use this only if re-adding Gmail produces an IMAP, authentication, or synchronization error:

1. Close Outlook.
2. In the Google account’s Security settings, open Your connections to third-party apps & services > Microsoft apps & services.
3. Choose See details > Remove all access > Confirm.
4. Open Windows Credential Manager > Windows Credentials.
5. Under Generic Credentials, expand entries beginning with MicrosoftOffice16_Data:OAUTH2.
6. Remove the two entries for the affected account whose full names include tp_google_imap_Oauth2.
7. Reopen Outlook and complete Sign in via browser, ensuring the Gmail-access permission is selected.

Microsoft documents this authorization and credential reset for Gmail sign-in and synchronization failures in classic Outlook.^4^

References

1. Create an Outlook Data File (.pst) to save your information
2. Remove or delete an email account from classic Outlook for Windows | Microsoft Support
3. Remove a profile in classic Outlook | Microsoft Support
4. Unable to add a Gmail account to classic Outlook | Microsoft Support