"HCW8064 - The HCW has completed, but was not able to perform the OAuth portion of your Hybrid configuration"

Hi Experts,

We are trying to configure Hybrid Mode on Exchange 2016 CU15 but keep running into HCW8064 concerning OAuth at the completion of the wizard.

I've read quite a few articles about the error which all seem to refer to Exchange 2013, nothing about 2016. Also been through all the logs but not finding much in there. There are a lot of steps involved in manually configuring OAuth so wanted to avoid that if possible.

Full error reads, "Configure Intra-Organization Connector. HCW8064 The HCW has completed but was unable to perform the oAuth portion of your Hybrid configuration. If you need features that rely on OAuth, you can try running the HCW again or manually configure OAuth using these manual steps."

Thanks.