Issue Migrating a Site from host to host

[epchost]

I have followed the documentation on moving a site on the following page:

https://docs.cmsmadesimple.org/moving

However my site will now not load and it is stuck with the following error:

[Mon Aug 10 11:05:10.652490 2020] [proxy_fcgi:error] [pid 29082:tid 140220909332224] [client 195.54.160.66:43997] AH01071: Got error 'PHP message: PHP Fatal error: Uncaught Error: Class 'CMSMS\AdminAlerts\TranslatableAlert' not found in /opt/bitnami/apps/cmsmadesimple/htdocs/lib/tasks/class.CmsSecurityCheck.task.php:32\nStack trace:\n#0 /opt/bitnami/apps/cmsmadesimple/htdocs/lib/classes/class.CmsRegularTaskHandler.php(130): CmsSecurityCheckTask->execute(1597057510)\n#1 /opt/bitnami/apps/cmsmadesimple/htdocs/lib/classes/class.CmsRegularTaskHandler.php(184): CmsRegularTaskHandler::execute()\n#2 /opt/bitnami/apps/cmsmadesimple/htdocs/include.php(274): CmsRegularTaskHandler::handle_tasks()\n#3 /opt/bitnami/apps/cmsmadesimple/htdocs/index.php(71): require_once('/opt/bitnami/ap...')\n#4 {main}\n thrown in /opt/bitnami/apps/cmsmadesimple/htdocs/lib/tasks/class.CmsSecurityCheck.task.php on line 32'

Does anyone know how to solve this please.

Many Thanks
Ben

[DIGI3]

A few guesses, it's hard to know without more information:

-cache wasn't fully cleared (you can manually clear it in the file system)
-hardcoded paths in the config.php file (not needed for recent versions)
-antivirus software has delete a file or files
-mod_security is enabled
-the transfer was corrupted (make sure you didn't transfer uncompressed files via ftp)
-unsupported PHP version (what was the old one, what is the new?)