When you see the Gmail temporary error 404. I will suggest you to open your url on the incognito window. now check if it is loading there or not. If your Gmail account is working fine, it means this a problem with the browser. to do that, you need to make these changes.
1. open the browser.
2. Go to the settings.
3. Select the Reset browser option.
4. Click on the restore to original default browser.
5. Click on the Done button.
