If you see error similar to this:
"Undefined symbols for architecture arm64:"OBJC_CLASS$_CXCallObserver", referenced from:objc-class-ref in SENTSDK(SENTCallHandler.o)ld: symbol(s) not found for architecture arm64 "
It means that framework is not included. Please check step 1 in the iOS Quick start or simply:
Go to your Project
Select your Target
Go to Build Phases
Open Link Binary With Libraries
Press + to Add the SENTSDK.framework (use Add Other button if needed)