EDIT 9/19/2023: This blog post has received significant update.
In this second part of the Demystifying Hybrid Free/Busy, we will cover troubleshooting of Hybrid Free/Busy scenarios, more specifica...
Updated Sep 19, 2023
Version 16.0
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Mirela_Buru
Microsoft
MicrosoftJimmyP1000 , this would require a support case to investigate.
Are Company A and Company B in hybrid organization or they are separate? or is company B in hybrid (some users in onprem and some in exo) ?
If A and B are not in Hybrid, then they are probably using Organization Relationships for Free/Busy and Sharing Policies for Calendar Sharing 1:1. So you would need to check Get-OrganizationRelationship both sides and make sure they are configured right. You can send me the outputs in a private message so that I can double check or upload them in the support case. You would look at Target Address Domains (From and To SMTP domains), if org relationship is enabled both sides, if targetautodiscoverepr or targetsharingepr are correct set, if free/busy access specified on the org rel is not restricted. You can check config part in first part of this blog.
Then, not sure what is the command you ran for Oauth token, I assume Test-OauthConnectivity. This is not needed if the organizations are not in Hybrid deployment with each other. Only in Hybrid we use Get-IntraOrganizationConnector for Free/Busy.