Sometimes Inspect can have trouble finding the Safari tabs on your iOS device.
The following steps unblock 80% of our users:
Did you restart your iOS device after enabling Web Inspector?
If you are using Windows, did you install and start iTunes to make sure your iOS device is paired with your computer?
Make sure your iPhone is unlocked.
Make sure Safari or the app you are trying to debug is the active one
Disconnect your phone
Connect your phone again.
As ironic as it might sound, but some users have needed to restart their Windows machine after installing iTunes. We suspect this is to start the Apple Driver provided by iTunes as a Windows service.
If your issue persists, please contact support and we are more than happy to help.