Unable to access Magento Admin Panel

[BabyRice]

I have no idea what has happened but I can't get on to one of my Magento Admin panels (Staging site).

Can someone provide me with a check list to try and get to the bottom of it.
Thanks.

[RommmKa]

If you have the SSH access - create other user from CLI then log in and change current user credentials:

php bin/magento admin:user:create --admin-user='new_user' --admin-password='newpassword123' --admin-email='test@test.com' --admin-firstname='New' --admin-lastname='User'