On one of my client's websites, We noticed MVIS was no longer communicating with "home" and unable to complete scans. I quickly realized MVIS has been replaced by SECURE. So I migrated them to SECURE.
I disabled the MVIS plugin, and then installed SECURE. After making sure the database backup was complete, I enabled SECURE. No problems, until I was presented with the 500 Internal Server Error during the Acceptance page and first time scan.
Typically the URL attached to the admin.php?page=mvl_wp.php <-- just leads to the 500 Internal Server Error.
The website itself continues to function, all I have to do is delete the whole admin.php?page=mvl_wp.php URL, and just refresh. Could this be a problem from moving from MVIS to SECURE?