O365 Calendar Integration throws error after following guide exactly

I followed this KB guide exactly, copying and pasting the Powershell commands (and replacing names where instructed). When I try to connect the O365 dedicated service account it throws the following error:

"The request failed. The account does not have permission to impersonate the requested user."

My predecessor set up a connected service account before, so there is already one set up for our current Zoom Room, but it doesn't look like the guide was followed. I'm guessing least permissions were not set up. I'm tempted to remove the existing account to see if that helps, but if it doesn't work, then I'll have broken my existing Zoom Room.

Any help from Zoom or anyone else would be great. I don't know much about managing Exchange Online with powershell. My support is through Lumen, and their support channel has not been very helpful so far.

Edit: It was a browser adblocker extension that was causing the error. Once I realized it was on (in the Private window, as per the guide's instructions) the service account added without error.