A hard-reset / Factory reset ( Pushing the reset whole button behind the modem ) should fix this issue.
Please be advised that once you do a hard-reset / factory reset you will need to re-configure the modem's settings which includes the Wi-Fi username/password.
Fortunately, we already have it posted here in our Community. Please visit the link below.
In case you need clarification please let me know I would love to help.
tpg tech come out done all testing and it was a not compatable with tplink-vr1600v on other modem fine so went bought a panasonic handset which seems to work tpg are montring my service and looking in to it further as to why not compatable i very happy with tpg as they went out of there way to get all working so thank you so much for all you people have done