Problem with Sink Combine

For some reason, the value on self?.isPresented = false only works when i insert a print inside my receiveCompletion...someone can help me with this problem? I really didn't understand the reason
service
.someFunctionHere()
.sink(
receiveCompletion: { [weak self] _ in
self?.isPresented = false
print("\(self?.isPresented)")
},
receiveValue: { _ in }
)
.store(in: &cancellables)