"Invalid hostname" error
The actual error​
If you see errors like
or

you are in the right place!
Checklist​
1. Check the domain you join with​
In this example we say that we want to join to our server using play.example.com.
I set up a CNAME record on play.example.com correctly, the problem is that i forgot to add
it to our domains tab in our panel.
2. I did not add both SRV and CNAME domains to our panel​
If you have a SRV record pointing to another CNAME e.g. _minecraft._tcp.example.com (SRV)
pointing to play.example.com (CNAME) you need to register both play.example.com and example.com
in our panel.