Problems detect beacon iOS 11

We have problems with the detection beacons, We use monitoring and didEnter function returns nil in major and minor.

This it’s us code:
print(String(describing: region.proximityUUID) + “:” + String(describing: region.major) + “:” + String(describing: region.minor))

We have EstimoteSDK version 4.25.1 , We installed it with Pod.
We test the app in iOS 11 device.

Can anybody help us?

Best Regards,