Gear VR Services cannot recognise "Samsung S10+" as being in "developer mode". Any solutions?

Hi there,

To begin, my main purpose was to install a custom Unity created app in my Samsung Galaxy S10+.
The App has been tested with Note 8, S9, S8 and Oculus Go and works perfectly.

steps to failure:
- I set S10+ to developer mode and enabled usb debugging.
- S10+ 's devices Osig file was downloaded correctly (double checked it) and put in Unity project (as other phones osigs)
- App installed in S10+ and launched... didn't run and throw the "not signed" (Thread Priority Security exception...) message that is thrown when there is no osig file in app.
- Tried to enable VR Services (Storage --> Manage Storage --> multiple taps on VR Service Version). The window showing activity with some files Loading started normally but failed with a message "You are not a Developer!"

So, Oculus app is signed in with Oculus Developer Account.
Device has been set to Developer Mode properly 
-BUT-
Gear VR Service tells me I am not a developer


I also tried:
Re-install Oculus app (from scratch) and Gear VR Services (--> deleted all updates).
Multiple reboots after every action and trial
Disable, clear cache  and re-enable gear VR Services

Any thoughts for further action or what I might do wrong...?