Monitoring client connections on a cisco C9800-CL with 2.0.0p17 (CRE)

You can try to change this line and hope it will work already:

to
detect=matches(OID_sysObjectID, r"^\.1\.3\.6\.1\.4\.1\.9\.1\.(2530|2391)"),

The searched values should be below the oid tree .1.3.6.1.4.1.9.9.512.1.1.1.1 for the SSIDs and below the oid tree .1.3.6.1.4.1.14179.2.1.1.1 for connected clients.