Try this solution
Find Spammer on Plesk Server
If the Spam is from a compromise Account you can easily find it using the command
zgrep 'sasl_method=LOGIN' /usr/local/psa/var/log/maillog* | awk '{print $9}' | sort | uniq -c | sort -nr | head
The error is because you have "Python support" enabled for the service plan but the component is not installed on the server. If you are not using python there is nothing to worry about it.
mod_python is not enabled by default you need to install it.
Is there a file called /usr/local/psa/admin/plib/Template/Variable/AbstractCachedData.php
just check with the command
ll /usr/local/psa/admin/plib/Template/Variable/AbstractCachedData.php
It looks an issue with nginx and some subscription try to disable nginx on both server and remove any subscriptions from new server and try again.
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Is it showing anything in the logs ? Check Nginx and and apache logs of thin time when this happened also you can reinstall nginx from Plesk packages
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