Please feel free to delete this if it is not allowed, but I spent the entire day yesterday trying to debug my new installation, and I found a solution, so I wanted to post it here in case it might help someone else.
I thought there were a bunch of problems with the installation because I was getting a bunch of different errors, depending on what I clicked on. These were the errors:
“The current role does not have access to this operation”
“An unexpected error occurred. You may have been logged out. Please reload the page and try again.”
“You are not authorized to access the requested resource.”
“Failed Ajax request or invalid JSON returned menu”
“Cookie OJSSID has been rejected because it is already expired.”
There were not errors in my php logs or my site logs. Eventually, I noticed a 403 error when I was using the Google Console and it tried to execute POST or PUT requests.
It turned out it was my Sucuri firewall that was blocking requests. When I disabled it, it fixed everything!
I hope this helps someone else if they are searching this forum for any of these error messages.