You can investigate the problem yourself:
On the watch face swipe down and disable wifi and bluetooth. Then select settings, then connections and make sure "Mobile network" is enabled e.g. by selecting "auto". Now, your watch can only access the internet using LTE. Try any app e.g. play store to test if you have access to the net.
If you cannot access the net, then check subscriptions. If this correctly shows EE, then most likely EE is the cause of your troubles, or else redo the subscription setup.
If you can access the net, then observe that your watch has two phone numbers: One shared with your mobile phone, and one for the watch only. Now call the latter: This should be independent of the complicated logic redirecting calls to your different devices. If this fails, it is likely caused by EE. If it works, then the error relates to the logic provided by Samsung / the supplier of the redirection technology. As a work-around you can redirect calls manually to your watch by on your phone keying "**21*xxxxxxxx#", where xxxxxxxx is the number dedicated to your watch.
