Hi, my new sim is not recognised. Normally I get a message to unlock the sim - it's not appearing. I have tried the new sim in my phone - it is working. I have tried my phone sim in the modem - it is

Hi Folks, I put a new sim in my TL-MR6400 modem and it worked perfectly at home. I am now in a summer house, and I am having problems. I can only connect by Lan cable - wifi doesn't work. In my iphone