Demystifying Hybrid Free/Busy: what are the moving parts?

Hello, Thank you for this hearty article. however I have the same problem. my Onprem users cannot see Online rooms or online user availability. on owa the OnPrem users can see all the online rooms but on outlook desktop they only see the OnPrem rooms. could you help me solve this problem ?

OnPrem

Windows\system32>Get-OrganizationRelationship |FL Identity, DomainNames, Enabled, Free*, Target*
Creating a new session for implicit remoting of "Get-OrganizationRelationship" command...

Identity : On-premises to O365 - 3cab0bd4-b6bc-4ed-xxxxx....
DomainNames : {myDomain.mail.onmicrosoft.com}
Enabled : True
FreeBusyAccessEnabled : True
FreeBusyAccessLevel : LimitedDetails
FreeBusyAccessScope :
TargetApplicationUri : outlook.com
TargetSharingEpr :
TargetOwaURL : http://outlook.com/owa/MyDomain.com
TargetAutodiscoverEpr : https://autodiscover-s.outlook.com/autodiscover/autodiscover.svc/WSSecurity

Online

PS C:\Windows\system32> Get-OrganizationRelationship |FL Identity, DomainNames, Enabled, Free*, Target*

Identity : O365 to On-premises - 0f1e6abe-beea-40ea-bc26-xxxxx
DomainNames : {MyDomain.com}
Enabled : True
FreeBusyAccessEnabled : True
FreeBusyAccessLevel : LimitedDetails
FreeBusyAccessScope :
TargetApplicationUri :
TargetSharingEpr :
TargetOwaURL : https://mail.MyDomain.com/owa
TargetAutodiscoverEpr :