Kevin updated his BlackBerry to the new 10.3 OS and now some of his apps don't work. Kevin did a "sideload" to update his phone, and Leo suspects the issues he's having is due to the carrier, namely Verizon.
When sideloading an OS, he's not getting the approved carrier edition of the operating system, but the version directly from BlackBerry without Verizon's customization. It's likely that it's an APN setting issue within Verizon's servers that is causing connection issues with Kevin's phone. This is why sideloading can be problematic.