For some users, Google's Pixel and Pixel XL devices have been having some issues with LTE Band 4. the problem basically manifests in not being able to connect to LTE if the connection is Band 4, which naturally might cause some frustration if you were expecting to get a faster internet connection. According to some users on the Google Product forums, the update to Android 7.1.1 Nougat is fixing this issue. Having said that, this doesn't mean that everyone will have the same results, but it's entirely possible that anyone with the LTE connection problems on their Pixel or Pixel XL could find a fix with the update to the latest Android software.
If you haven't received the update to Android 7.1.1 Nougat just yet, the updates only just recently started making their way to users, after following the Factory Images and OTA Images having been posted by Google just this week. Unfortunately because the OTA updates will be a somewhat slow rollout to reach everyone, that means that it could still be a little while before some users with the issue will see a fix, but the good news is that the Factory Images and OTA Images can be flashed so the update is installed manually, which means no waiting.
The connection issues are not new as of today but were rather first noted by those having the problems back in November. With this being the case, it also seems that Google has been well aware of the issue, as Google seems to have noted in the forum post that they have been working with carriers to ensure that LTE works correctly, which according to Google consists of carriers supporting the Pixxel's proper LTE bands. Issues like this may not be expected by most users, but it shouldn't be a major shock when these sorts of issues arise as these things do happen. This also wouldn't be the first issue that has popped up with the Pixel and Pixel XL, as users in the product forums reported recently about issues with the camera app freezing and causing glitchy photos. Luckily, that issue too had caught Google's attention and a fix is now being worked on for it.