I have been using Lightrom app on an Android phone for a few months, with auto import enabled and an album selected as import destination. Until a couple of weeks ago, it's been importing photos from my smartphone in background (i.e. without having to open the Lightroom app). Recently I realized that, since a couple of weeks ago, no photo was imported from the phone, neither in background not by opening the Lightroom app.
Trying to solve the issue, I did the following:
a) delete all Lightroom data from the phone, log in again and re-enable auto import => no changes
b) create a new album as set this as auto-import destination => photos from the phone camera are now imported if I open the lightroom app, but still no import happening in background
I was informed about an update of the app two days ago. Now the automatic update works again on my phone. WhatsApp pictures don't have dates and more but that's less important for me compared to the automatic upload not working. Hope it works for you as well.