What does it mean?
If you reach this 403 Forbidden screen, you may have incorrectly entered your HTTP AUTH Password.
Alternatively, you may have entered your WordPress admin details here by mistake.
When presented with this pop up (see screenshot):
You must first entere your HTTP AUTH login credentials.
After this step, you will be presented with the normal WordPress login screen where you can enter your WordPress Login credentials.
Your HTTP AUTH username & password was sent to you in the original 1password login link.
These details are different from your WordPress admin login. The reason for this extra security step is that it helps protect your WordPress site from bad actors and malicious users who may attempt to gain admin access and control of your website.
What should I do to fix it?
Clear your browser's history according to the following instructions:
If this error occurred within the last hour / two hours / etc you can choose that shorter timeframe to keep items in your browser history, if you like.
Once the history is cleared / another method is chosen (see the next paragraph Troubleshooting), then you should be presented with the HTTP AUTH login screen again.
You can now enter your HTTP AUTH login username & passwords as sent in the 1password document. THIS IS NOT YOUR WORDPRESS LOGIN CREDENTIALS
Once this extra security step is bypassed, you can now enter your normal WordPress logins.
If after clearing the history, this 403 screen is still reached, clear your entire browser history "since all time" / "everything"
If you don't want to clear your entire history, you can try incognito mode OR another browser application.
You can access the login screen, but your login doesn’t work? Then simply follow the “Lost your password?” link to reset your password. Make sure to check your spam folder for the reset password email.