I've seen a few reports of success with this combination but I'm having no such luck. So I'm hoping those with working configurations could spill the beans on what success looks like.
In particular, has anyone used the 7800NXL specifically (not that it should matter?), and the E3372h-608 specifically? The -608 has software version 10.0.5.1 instead of the usual 22.xxx. I don't think it should matter, since 22.xxx is still HiLink, but I'm at a loss.
What does your 7800 status/configuration page look like? My 3G/LTE seems to expect a modem to dial (ala stick mode), and reports it can't find one. What appears in the log when you plug the dongle in? I see mine trying to enumerate as mass storage, ethernet interface, and AT modem in turn, and seemingly giving up on all.