Cable modem wont connect to internet?

i have a cable modem that i switch from room to room whenever I want to play the game or go on the computer anyways last night i was playing the game fine and this morning i brought the modem back to the computer room and now im trying to play the game agian but the modem will not work. So i try to see if itll work in the other room and it does i tried switching the modem back to the game room already like 5 times and it doesnt want to work but in the computer room it works fine. This is the first time this has ever happend to me and ive been doing this for about 5months now.

 

i think the modem uses mac address to authenticate your internet connection from your isp there is possibility the modem can recognize the mac address of the computer that is why its getting internet connection there a possibility I am not sure but for the other device to work w/ modem you need to register its mac address to your isp.