Tired by the impossibility to use the updated IOS app, finally i decided to update my ipad to ios to 12 and voila now WP is working as expected!
Before i was still on IOS 10 because i don't like to stop using some old 32bit apps only because apple decided as it.
Now i made the sacrifice in the name of WP, but please next time advise that app is working only on ios12 or flag it so that is not possible to install in a different system....
For your information on previous ios 10 all the boards, calendar, hit screens appeared as a blank screen
Same behaviour on app and safari.
Customer support service by UserEcho