Free Busy - From Cloud to on-premise not working

Hi everyone,

we have set up an Exchange hybrid configuration.

Everything works fine. Except the Free/Busy from Cloud to on-premise.

I read some (also opposite) blog posts and decided to follow this one:

https://blogs.technet.microsoft.com/exchange/2018/02/06/demystifying-hybrid-freebusy-what-are-the-moving-parts/

We have executed the HCW therefore ended up with 

IntraOrganizationConnector

OrganizationRelationship

and the Other one ;)

I have checked the availbility of the autodisover from external with the MS connectivity test.

I tested the Oauth from Exchange online (Test-OAuthConnectivity -Service EWS -TargetUri etc)

I checked all URLs in the connectors

What else can i do or check? The TargetSharingEpr is empty. But according to the blog this is "normal". Other MS sites states this must be filled (for OrganizationRelationship). Other blogs set the IntraOrganizationConnector to "Enabled:false"

Can someone advise?

Thanks Stephan