Not getting data from Xmanager/Detector collection has two likely causes:
1) The Detector collection for that DB2 subsystem is not active.
2) The CA SYSVIEW for DB2 Data Collector parameters in *.SOURCE(IDDCPRMS) member do not specify the correct XMANID.
First double check the Detector collection was started for the DB2 subsystem.
Second in your CA SYSVIEW for DB2 Data Collector output locate the following messages.
DBG02177I ... INVOKING PARMLIB READER USING "EP=PTTDUMMY,SUFFIX=xx "
DBG02179I ... PARMLIB OPTIONS USED: PTISYSxx, SETUPxx, PLANSxx, XMID=nnnnn
If this is not correct, you should update your SUFFIX= parameter in *.SOURCE(IDDCPRMS) member to point to the correct Xmanager parameters. Or review the SETUPxx member in PTIPARM data set and double check the set up is correct.