The first thing to try is a forced restart. After that the next thing to try is whether you have the same issue on a different network to rule out router issues on a specific network.
If it does not work also on a different network, contact Sprint and if Tier 1 support cannot help you escalate it to advanced support.
It is possible the issue is specific to your phone but without doing a lot of testing there is no way to know for sure. Since it was working fine and now is problematic with a software update the odds are there is a conflict somewhere that is not specific to your phone but may be specific to the model.
The more likely scenario is that there is a conflict between the carrier profile and iOS 11.2 that is impacting the functionality of that feature at least on your model.