Ops Server can't comunicate whit Master Server

Hi,

 my OPS Center did not communicate whit Master (have work fine for 4 years).

I've tried to remove and add master but i have this error message

OpsCenter-10905:Action not permitted. Please verify that the OpsCenter host is listed in NetBackup configuration file (host properties or bp.conf) and/or trust is established in case of NBAC.

Ops is on host properties of master

I don't understood the part about trust.....