Netbackup issue when backup oracle using RMAN

Dear All,

I encounter the problem on the RMAN backup script on the server with the below error

ORA-19506,ORA-27028, ORA-19511.

I check the log related with the Media Manager Layer (MML).

ORA-19506: failed to create sequential file, name="TIAEEG_dbf_1267_1_1039024505", parms=""
ORA-27028: skgfqcre: sbtbackup returned error
ORA-19511: Error received from media manager layer, error text: <<====
VxBSACreateObject: Failed with error:
Server Status: Communication with the server has not been initiated or the server status has not been retrieved from the serve
}
 

Can you advice if there is any solution to fix it? 

Many thanks