Our problem went away after installing the update and restarting my computer. The service started automatically and I had no more issues with the License Manager UNTIL...
Friday, Aug. 2, I get the message on my machine again opening AutoCAD 2020. But not just mine, on the other 2 computers which were using either 2019 or 2020. The difference is we got a dialog box that had activation three options: Single User, Network License, and Exit (I think if I remember correctly). Clicking on the Single User option cause AutoCAD to show it was processing for a bit but then give the error message again. We don't use network licenses (and never have).
We also (coincidentally?) received the email below at the address used for the Autodesk primary account about the Account User Management.
I checked our account online and all the users were still there and authorized to use the software. Since I didn't know what else to do, I closed AutoCAD, logged out of the AutoCAD Desktop App, and restarted it (I stopped it by killing the process in Task Manager). I'm not sure restarting it was necessary, but it just took 30 seconds and I figured I might as well. I logged back in to AutoCAD Desktop and started AutoCAD. It either started up right away or with the three-option dialog again where I clicked Single User. After that I've had no problems. I looked at the licensing in the About dialog in AutoCAD and instead of a license number it shows "Autodesk ID" then my login.
I hope this helps!
Aug 2 Autodesk Email about Account User Management
Aaron Meyer, PE, LS
Meyer Civil Engineering, Inc.
Bakersfield, CA