Please first test the connection between your transceiver and the OS2 using the built-in local echo feature:
http://manuals.sharkrf.com/openspot2/en/control-calls.html#local-echo-service
Make sure you've read the P25 transceiver setup section in the user manual:
http://manuals.sharkrf.com/openspot2/en/setting-up-your-transceiver.html#p25-radio-setup
Make sure your transceivers are not using a talkgroup-based squelch (selective squelch), or if they are in use, make sure the talkgroups you want to use are in the selective squelch list.