From your description, you installed and tried to authorize ArcGIS Desktop Single Use. You mentioned you received a trial license from MyEsri. What is the name of the file? It's possible you received a license file for ArcGIS Pro and not ArcGIS Desktop. You can also test by going to back to the ArcGIS Administrator. Click on the Supported Operations folder and then Deauthorize. On the second dialogue, it will list all your authorized Single Use license. If it has the word "Pro" in the feature names, it's a Pro license which cannot be used for ArcGIS Desktop.