That is strange. There is no reason that shouldn’t be working then. Maybe check the settings in the device you are trying to tether to, make sure it doesn’t have manual IP or proxies or anything setup as that could stop it, try deleting and reconnecting, and if still nothing try resetting the network connections on the device you are trying to tether to.
Yes it is something in Boosts system settings but they won't admit it. There is another post from back in 2015 about the same problem. All the comments on that thread had the same issue. I don't know why they won't just fix it.