While testing I found below issue while accessing OPSVIEW panel- Option 6 Command:
"Cannot find program OP600000 in SYSEXEC"
Other possible message if the DD SYSEXEC is not even allocated to the TSO session:
Cannot find program OP600000 SYSEXEC DDNAME is not allocated
Another symptom of the same problem is when when trying to access the COF Screen (Option 4.12 from the OPSMVS menu):
"Cannot find program OP412000 in SYSEXEC"
The OPS/MVS library CCLXEXEC is not allocated to the SYSEXEC concatenation of the TSO user.