Try Knowledgebase Solution ID 94847.  Very similar to what you tried, but you need to stop and then start the Sage CRE Hosting Framework service first.

When I go to Sage Admin - then services management from that Solution ID instructions, it tells me application not licensed

When I go to Sage Admin - then services management from that Solution ID instructions, it tells me application not licensed

I'm not sure if you understood, but Sage CRE Hosting Framework is a service that runs on the server.  (It's not the Service Management application.)  You get to it by typing Services.msc in the run box at the bottom left side of your screen.  When it opens there are many services running on your computer.  Find Sage CRE Hosting Framework and highlight it.  Then you'll see a "stop" button you should click.  After that finishes, then you'll see a "start" button you should click.  Then you'll go into License Admin and do what you did before..   (Our server is Windows Server 2019 and now finds services simply by typing services in the run box and it populates a list and it is a desktop app that looks like a gear or sprocket.)   

No, I understood.  That's exactly what I did and I'm still getting the same outcome on sage desktop. 

  I may have misunderstood.  It sounded like you tried to start Sage's Service Management application and got a message that told you that you aren't licensed for Service Management.

Did you get to a screen that looks like the second screen?

yes.  when I click on the sage 300 cre hosting framework, I right click and select stop.  a small box appears and says service control and gives me loading style box, completes and disappears.  then I click on sage 300 cre hosting framework again and select start, same steps as select stop. 

Then retry license administration on the server like you did before and update the license.  We've used this on every upgrade from Vs. 17, 18, 20.3, and now 20.5 and it's worked.   From the server, maybe starting Sage Desktop-Options - License Administration is better than opening programs - Sage Administration - & License Administration.  I mean stranger things have happened. 

I've done that as well 3-4x as well.  with desktop opened and with it closed.  restarted my computer each time. 

Sage License Administration:

Knowledgebase

Solution ID: 91168

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Solution ID: 94847

Solution ID: 92866 Special characters in company name can be a problem

Solution ID: 86855