Customers who have had this issue and similar network and GPS connection issues have almost always found that resetting the network on the phone and waiting a few minutes resolves the problem.
To do this, go to Settings > System > Reset options > Reset Mobile Network Settings
also, while in Reset options, tap on Reset Bluetooth & Wi-Fi.
Within the text messanger settings, you must also ensure that you have Group Messaging turned on. To do this within the default Messanger app on the device, go to Settings > Advanced > MMS Group messaging
Simply restarting the phone will NOT do the trick. Although doing so does resolve most issues with apps not working properly, you must follow the above steps to reset the network connections.
In some rare cases the carrier must be contacted so that they can also reset the number and connection on their end as well.
NOTE, contacting the carrier and telling them you're having this issue will take A LOT of time unless you specifically ask for an advanced technician. Their front line support / sales personelle are next to useless when trying to trouble shoot most all problems you may have with the phone as they are simply not experienced in doing so. Demand you talk to an experienced service technician and bypass their front line Tier 1 support people!