The
history of the 3G type is that after a certain date the firmware was changed. Before the change a 3G and BR24 was so to say equal at least about the communication interface. After that date the command interface is more like the 4G. Just more like but not the same. Unfortunately I don't remember when it was changed. I've rather new 3G and it works in radar_pi set up as a such. But I suggest you try to set it up as a BR24 type in radar_pi and check.
BTW what's your firmware date? Could be read in "Info" window if the radar was started up while the plugin is active.