You can easily confirm that the BigFix Client is properly receiving notifications via either the Client log (look for lines containing things like ‘GatherHashMV command received’), or even via property/relevance (ex: https://bigfix.me/relevance/details/3021681). Here’s an additional topic on this to potentially review: TCP/UDP port query
If you find that notifications are not getting through for some reason, you might consider command-polling, or even the new persistent connections feature introduced with 9.5.11: https://www.ibm.com/support/knowledgecenter/en/SSQL82_9.5.0/com.ibm.bigfix.doc/Platform/Config/c_persistenconn.html