My new comcast xfinity triple play can't connect tablet

It sounds like somehow the security settings for the tablet have been set to require a pin number to be able to get past the lock screen of the tablet. This has nothing to do with your new router/internet service.

Does the screen look something like this?



If this is the case and you do not remember the pin number, you'll need to do a factory reset which usually involves pressing & holding one of the volume buttons when powering up the device.