Clearly, the problem lies with the new router settings.
To see them, launch your web browser and type in the address, such as: http://192.168.1.1
and hit Enter. That address might be on the router's label and/or in the instruction leaflet.
Then type in the Admin name (usually "admin") and password (from the router's label).
That gives you access to the router's internal settings.
I suggest that you access the old router settings via a web browser and make a note of them (username & password). Username is usually (I think) your OTE email address.
Then connect the new router and access its settings menu via a web browser.
Ensure that the username & password are the same. If they are not, make a note of them, then change them to those of the old router and save the settings (if it's not automatic).
This video shows you how to access the router menu, although the speech is rather fast!https://www.youtube.com/watch?v=4m3XLIuf3z4