Can't assign new user to existing extension with no user attached to it

Hello and thank you for taking the time to reach out to us here on our Comcast Business Forums! I'm truly sorry to hear that you are running into errors assigning an extension. Just to confirm have you attempted the following steps:

1. Sign in to My Account and select Business VoiceEdge from the Services menu.
2. Navigate to the Site Dashboard and select Numbers and Devices.
3. The All tab lists all assigned and unassigned seats. The Unassigned Seats tab lists every seat not assigned to a Business VoiceEdge user. Select your desired tab, and identify the seat you would like to edit.
4. Expand the options icon and make the changes you would like applied. You can:
   • Assign a seat to a Business VoiceEdge User or Admin or Unassign a seat
   • Edit the E911 Address
   • Edit the Extension
   • Edit Device name

The full directions, including helpful screenshots, can be found by clicking this link: https://comca.st/3vJME0M

There is no Services menu on https://business.comcast.com/, I see a "Manage Business VoiceEdge" under both the "Subscribed Services" heading and the 9 dot square in the top left hand corner, I assume this is what I'm supposed to go to. When I go to that I see a "Manager Dashboard" but nothing that says "Site Dashboard" and none of the menu options or submenu options on this page show a section called "Numbers and Devices". I find the phone by going to Manager Dashboard > Business VoiceEdge phones > and clicking "Manage" on the extension. Under the "Assign a phone to a user?" dark blue section I try assigning the user account there and that's where the error occurs.