No good! Keep hitting "Unauthorised - Invalid Credentials" error...
How can that be? I was very sure I keyed in the correct credential of the 1st OpenAM in Step 1.
It was only after a while then I found out the cause. Our 1st OpenAM was already configured to authenticate with Microsoft AD by default.
The installer, by default, needs to communicate with OpenAM via the DataStore instance. So, we need to temporarily switch the AZAD instance back to DataStore.
And once the installer goes through, switch back to AZAD again will do the trick!