Please read this: https://manuals.sharkrf.com/openspot4/en/dmr-usage-notes.html#page-top
"Talkgroups and reflectors are network features, they are completely handled by the network and not the openSPOT4, and their behavior may be different on each network."
You have to start a call to the desired TG ID to make the server link it for you, or you have to configure the TG ID as a static link on the networks or servers web interface.