I'll be full of gratitude if you can share your test sample with 2 DEXTs with me (alkensox@g mail.com)...............For the casting, I've compared pointers to 'this' of the matched DEXT service and the pointer coming into matching notification. Seems they differ in some reason

Solved the error of missed notification by calling RegisterService in the beginning of the 'Start' method, before source/queue/notification setup @Drewbadour , seems now notification is delivered. But still have problems: ........... FIRST: Services are in the different processes. IOProviderClass = IOUserResources, IOUserServerName is $(PRODUCT_BUNDLE_IDENTIFIER) for both, IOUserServerOneProcess = 1 for both. IOMatchCategory equals IOUserClass for both. ............SECOND: When notification is delivered, OSDynamicCast fails to cast service to the type of my service. Probably the most important part