Did you receive a text/email to confirm your service had gone live ?. Are you able to log into the 'My Account' site to check the status of your activation ?
It would be worth going to the Service Centre to do a test on your phone line, this will indicate if there is currently a fault on your line. You can also access this from the ‘My Account’ site.
If you have a landline phone can you dial 17070, this will read back the phone number of the line, can you ensure this is the number you expect (i.e. the number displayed in 'My Account').
If the above checks are all ok have you tried switching the router off for over 30 minutes, then when you switch it back on it will start a new 'session' in the street cabinet, this can sometimes help it connect.
The TalkTalk staff on this community will also be able to help, they will hopefully be able to respond to this post within a working day or two. You may get faster support from the live chat or by phoning up during opening hours.