Do you have a computer connected by cable to wifi router? Is internet working on it?
Are the Wifi or 2.4G/5G lights on?
Is there a button on the router to enable wifi? On the back or top edge?
What model router is it? Wifi might not be enabled in the configuration.
Search around google. Like this one: https://whatsabyte.com/windows/dns_probe_finished_no_internet/
Change your default DNS server to a third party one. Such as Google's 126.96.36.199, 188.8.131.52 or OpenDNS's 184.108.40.206, 1,0,0,1. Let us know if it is still an issue.
If you have an iOS, can you download the My TPG app? Login to the app, go to Support -> Connection Status, and Test Your Connection when it drops. Pretty sure you can lodge a fault in there too but not too sure when you will get a response.
Post a reply and let me know if connection is fine but still drops out. Hopefully "Mod" can watch out for this thread. Worst case is you have to change the ISP.