res_pjsip.c:3142 ast_sip_create_dialog_uac: Endpoint '300': Could not create dialog to invalid URI '300'. Is endpoint registered and reachable?
chan_pjsip.c:2427 request: Failed to create outgoing session to endpoint '300'
app_dial.c:2510 dial_exec_full: Unable to create channel of type 'PJSIP' (cause 3 - No route to destination)
Please increase the verbosity (core set verbose 9), ensure it is going to the console in logger.conf, do a call attempt, and provide that. The version of Asterisk in use would also be useful.