Connection refused, code line 17

Hey guys,

I’m pretty new to all of this so please be gentle :smiley:
I wanted to run yourls via docker on a Synolgoy NAS and pretty much followed the instructions here:
https://www.synoforum.com/threads/link-shortener.822/

But I can’t get it to work, the log says:
Warning: mysqli::__construct(): (HY000/2002): Connection refused in Standard input code on line 17
MySQL Connection Error: (2002) Connection refused

Seems like I messed something up with the MariaDB configuration?
Any tips or hits are greatly appreciated!
Thanks.