Generate Azure Policy Compliance Alerts By Sending Custom Data to Log Analytics - Part 2 - Automated

I really do not know what role is needed for what principal in your situation.  Like I said, I do not currently have this setup this way to test so its hard for me to say without seeing it.

If you are in a time crunch, you could do those couple steps in the portal or manually to move forward.  That may actually show you more about what you are missing as well.

I would also check to make sure that you have the resource providers installed as well.  Given your error message, it is not likely the cause but its easy enough to check.  I would make sure that all of the RP's are loaded from everything mentioned in your error message(s).