That’s very interesting. I’ve not heard of this happening before. Any of the hotspot plans that are meant for those sorts of devices, at least new ones in the last year plus, have worked on just about any device as long as it is not brand new, and even then, the new devices get added pretty quickly.
Some of the tablet or hotspot plans issued on existing accounts or tied to Magenta or older plans won’t work on Peplink stuff. You have to have the newer hotspot plans, and in many cases, pre-paid is safer.
This has been an issue for a long while with MikroTik products. There are locked/unlocked versions of many of them, including the Groove. Many people wanted the unlocked versions because there were more options for power and control, but many US resellers were having issues getting them, or simply wouldn’t sell them to folks in the US. What the country designation does is unlock/lock certain bands for WiFi, so it can be useful if traveling abroad.
Generally speaking, buying MikroTik from Amazon is going to be a crap shoot. I’ve done it many times and have actually gotten wrong versions and DoA products. Buying from MikroTik resellers like Streakwave or Baltic Networks usually is a better idea if you’re looking for a very specific model.