Account changes usually take place overnight. It should definitely be there by now, so first lets try some basics with your YouView box and router:
Are you using a TalkTalk supplied router from the last few years?
What is your internet download speed? (supportal-test.co.uk)
Are you able to access the TalkTalk player and watch one of their free help videos?
Are you able to view the TalkTalk TV Test Channel? (Channel 900 or 999)
Have you tried switching both the YouView box and router off at the mains for a few minutes, starting the router and waiting until that has a full internet connection, then switching on the YouView box, while pressing and holding the plus and minus buttons on the front of the unit to load maintenence mode, and then doing a reset there?