If your logs also do have the same line as "unknown variable 'set-variable=max_connections=1500'. "
then please remove that line from the configuration file
Due to the configuration error, the MySQL server is aborting.
If you have any different errors then please share your logs here
or you can open a support ticket at https://softaculous.deskuss.com/open.php?topicId=3 for fatser solution of your issue.