I came to the same issue with my P900. Just realized that there might be connectivity issues with android 8.0+ and the WMU app for Android.
I have few devices u did try on and this is the result:
-Sam S6 T-mo (7.0) - yes
-Sam Note 3 - LOS 13.0(6.0.1)- NO
-Sam Note 8 (Int’l) (8.0) - NO
-Sam Tab S4 (8.0) - NO
-Nexus 7 (2013) LOS 14.1(7.0.1) - yes
-Hawei Ascend (4.4.4) - yes
- Iphone 6s (11.4.1) - yes
Pretty dramatic results! Most my old devices do connect without too much issues here.
Before I began by eliminating possibilities, I restored my P900 to factory settings and formatted the SD card. I also re-flashed firmware 1.5 fresh download; but nothing happens!
So, today I done loaded the WMU from play store to the rest of my devices and did not what to make out of it. Hope this helps determine what might be causing connectivity failures.