Suddenly Dorico cannot open on any computer because of this error: "A connection to the license server could not be established, either due to incorrect network settings, or because the license server is currently not available (e.g. due to maintenance work). Really?
Is this a common occurrence? I thought my license was installed on the USB eLicenser dongle. How can this be occurring?
If you launch eLC (to be sure as an administrator) and don’t proceed with automatic maintenance, what do you see? Do you have the appropriate license on it?
Unfortunately the eLicenser server is currently unavailable. I’m sorry for the inconvenience caused. The team are working to restore it to operation as soon as possible.
I’m working (offline) regularly since this morning. If I open eLC and don’t maintain I see all my licenses… 
Obviously, if you don’t have a valid license… you have to wait until the server will be up… 
About a week ago I had the following experience: Dorico (Pro, Windows 10) wasn’t opening, without any error message. I could open eLC and see my licenses. However, during maintenance, I got exactly the same message as you, @spheres ; I just assumed it was due to my then extremely poor internet connection (I was in the middle of a forest). So: Dorico wasn’t opening despite the fact that eLC displayed the licenses properly! In my case, for reasons unknown, Dorico started working after I restarted my laptop. Sorry if it’s too trivial, but on the 1% chance you haven’t tried it, maybe do so?
My (humble) advice is don’t maintain if you don’t have to do it (like when you have to download a new license…)
Thanks for the feedback. Since then, one of the computers is opening Dorico ok despite the fact that the eLicenser app is showing errors… A new Mac however is having all sorts of issues. With dongle installed, Dorico won’t open AND eLicenser also has errors.
As the new Mac has inherited its files from a TimeMachine backup, perhaps there is confusion at the permissions level.
However, I still don’'t understand why Dorico doesn’t open normally when the dongle is inserted.
You could try installing the latest version of eLicenser Control Center, in case the version on your Mac is somehow so old that it doesn’t recognise the Dorico license on the eLicenser, but that seems very unlikely to me.