Firstly which box do you have - is it the TiVo or the V6? If you're not sure, check here
Lack of a TV Guide is probably indicative of the box's regular connections failing, but you can check for yourself. Follow Home > Help & Settings > Settings > Network Connection.
In the top-left, does the box show a successful connection in the preceding 6-ish hours? If not, what's the error reason given? You can try forcing a "connect to VM services now" at the bottom, wait 10-20 minutes and recheck.
If that fails, then further advice depends which box you have, as they connect to the internet differently.
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