Hello @perry_the_platypus, welcome to the Quick Sight community!
I found some documentation that may be helpful in regards to debugging this issue. I will link it below. Let me know if any of it is relevant and what you are able to discover, then I can try to guide you further.
Testing SSL connection, Quick Sight Q&A:
A community thread where a user experienced a similar issue, lots of input about establishing the datasource connection from our experts:
Documentation about establishing a connection between MariaDB and Quick Sight. I didn’t find any direct reference regarding SSL though:
https://www.cdata.com/kb/tech/mariadb-odbc-mysql-aws-quicksight.rst
Also, for some more information, are you utilizing a VPC to establish the connection with Quick Sight? A little more information about how you connected to the database could be helpful in debugging. Thank you!