I can confirm the same issue, if there are more then 2 cascaded lookups, nintex mobile is not able to fetch items for 3rd and all the other levels.

I've tested it with nintex mobile version 3.9.3 on win10

and with nintex mobile versions 3.9 and 4.1 on android device.

in all three cases I experienced the same issue.

it sounds like a bug.

I have this issue with just two fields (FieldA and FieldB) with a cascade between the two.  Works fine in "Desktop" layout as advertised, but control just shows "Loading" and then flashes "Error getting list entries" at the top of the mobile form.

are you on current release with nintex mobile?

with recent releases there were significant changes to lookup functionality.

I have set up 4 levels of cascaded lookups on v4.3.3 and it works for me without any problems.

Yep on current release - turns out when I was following the recipe I threw in a dash of "site lookup column" when I was feeling creative.  Making sure I used a local list lookup column got me back on track.  Thanks to the support guy at Nintex for helping me think through the issue.

I've got the damn error message back again when I swapped out an AD User inside a SharePoint Group for an AD Group (containing that same AD User in it) inside a SharePoint Group.  Not sure if it's a coincidence, the timing sure happened very close together.  I'll try to circle back here and post an update.