Microsoft has updated the Xbox App for Android to a newer version than the version provided by the Oculus store during the Minecraft VR install.  If that version is present before minecraft vr install it is impossible to login to xbox live within Minecraft VR. The version included from the oculus store will only work one or two times before it will fail requiring noticing it needs a  newer version at which point xbox live login will fail again.

This blocks realm and network play and import of your own worlds. 

Device Samsung Galaxy S9 Plus

Gear VR 2017 

Microsoft Xbox controller connected via Bluetooth 

Os android oreo 8.0.0

Xbox App that Android installs 1805.0618.1637 dated 20 June, 2018 

Related bug MCPE-33156