Message just appeared - Could Not Activate Iphone, my iphone was activated a year ago!

Anyone had a similar issue? Picked up my iphone to use and there's a message on the front screen waiting for me about needing to activate my iphone. I also cannot get away from this screen to my main screen and have restarted a number of times. Now the message 'Could Not Activate Iphone' Try Using wifi and another button Try again over Cellular.. ***. My iphone was activated over a year ago. Ps clicking on the Try Again over Cellular button doesn't work for some reason even though it shows my carrier and coverage.

Anyone had this happen to them?

Regards