I got a data SIM to access the HSPA+/3G mobile data network on my Moto G2 (XT1068). Prior to this, I had never connected to any type of data network on my phone. To my surprise, I found that the phone would only get a measly GPRS or EDGE connection on this SIM! However, the same SIM inserted into another XT1068 and other phones got a HSPA+ connection without any problem.
I tried everything imaginable to figure out why only my phone could get a HSPA+ connection. Some of things I tried that did not work:
Configure the cellular connection configuration parameters manually.
Trying both the SIM1 and SIM2 slots. In reality, both of them should support 3G.
Factory reset of the phone.
I was at my wit's end when I thought of one final scenario. The phone had never connected to a data connection before. It has started out with Android 4.4.4 (KitKat) and had been OTA upgraded to Android 5.0.2 (Lollipop). Knowing how buggy software can be, I imagined a scenario where the upgrade was buggy enough to disable some variables of data connection since the phone had never done data before.
To try this final solution, I downgraded the phone back to KitKat as described here. I booted into KitKat and lo behold I got a HSPA+ connection on the data SIM! The phone then OTA upgraded again to Lollipop. However, this time it did not lose any data connection and I still had HSPA+/3G after the upgrade!