Hi. Have done that. I even went into the router and loaded factory settings. Keeps saying sim locked but nowhere gives me an option to unlock. Yet sim works in usb stick (modem) with no problems. So definitely on router side. No matter which sim I put in, it says sim locked. I will check tonight and get some screen shots to post. I know when you receive the router you have to put the code once to unlock, hence the code in the box. I didn't have to do it though as it was pre done when I received it (should be unlocked forever, so they say).
I tried with sim, without sim, no place to put a code.