https://www.ads-software.com/support/topic/setup-steps-troubleshooting-steps-uninstall-steps-requirements-compatibility?replies=1
See the Custom Code Note.
htaccess File Troubleshooting Steps: Unable to Login to Your Website:
1. Use FTP or your Web Host Control Panel File Manager and delete the .htaccess file in your website root folder and the .htaccess file in your wp-admin folder.
See Custom Code Note
2. Log into your website, click the BPS AutoMagic Buttons and Activate all BulletProof Modes.
Custom Code Note: If you have isolated a problem to the root or wp-admin .htaccess file and you have added additional custom .htaccess code or additional .htaccess code from another plugin to BPS Custom Code then cut (not Copy) all of your additional custom .htaccess code out of all BPS Custom Code text boxes and save that custom .htaccess code to a Notepad or Notepad++ text file, Click the Save Root Custom Code button (or the wp-admin Custom Code button), click the AutoMagic buttons on the Security Modes page and activate BulletProof Modes. You can then further isolate which custom .htaccess code is the problem by adding only 1 block of additional custom code back to a BPS Custom Code text box at a time.
If the problem is not being caused because the root htaccess is not allowed to be locked on your host server or that there is bad/invalid custom htaccess code in BPS Custom Code then you want to check file|folder permissions and if you have a DSO Server Type then you want to make sure all of your WordPress folders have the same Owner UID. You can check that on the BPS System Info page.
