Connector authentication failed means you are not using the correct server password. Please check the hotspot security setting on your BrandMeister SelfCare page at
https://brandmeister.network/
If hotspot security is turned on, you have to use the hotspot password you've set there as the server password in the openSPOT. If hotspot security is turned off, then you have to use the default server password which is "passw0rd" (without the double quotation marks).
The server echo will only work if you are connected to the server (there's no authentication failed error message and the status field on the Status page displays "connected").
First test the connection between your transceiver and the openSPOT2 by using the OS2's built-in local echo service on DMR ID 9999.
http://manuals.sharkrf.com/openspot2/en/control-calls.html
If you do not hear yourself back correctly, then make sure you've ran DMR AutoCal, or manually change the RX offset setting on the Modem page for the lowest BER.