Connection problem moving from MariaDB5 to MariaDB 10 on Synology NAS

I have a working C# .NET application that connects to a Synology NAS with MariaDB5. I need to access to the functions in MySQL version 8 so have tried migrating to MariaDB 10. I've installed MariaDB 10, imported the database, created the user, granted permissions but it won't connect. I've stopped MariaDB 5 and even uninstalled it but it still won't connect. I've changed the port number in the connection string to 3307 but can't find anything else that should be changed in the connection string.

The only difference between 5 and 10 installs is that you get the option to allow TCP/IP connections when you install 10 so not a lot to go on with that.

I've reverted back to MariaDB5 starting from a clean install and everything works again fine.

Are there settings within the Synology NAS that need changing or is this a connection string issue?

First time posting on the forum so apologies if I've put this in the wrong place etc.