If your computer can support a more recent version of Dorico (and since you’re on Windows, that should certainly be the case), it would be a good idea to update to the latest version of Dorico before the eLicenser servers are switched off.
If nothing else, you will be free of these kinds of problems with the Soft-eLicenser not being reliable on your computer, because Dorico 4 and later use the newer and much more reliable Steinberg Licensing system.
You will also of course benefit from a lot of new features and improvements added to Dorico since May 2020, when Dorico 3.5 was released.
If you are worried about the cost of updating, if you start a 60-day trial of Dorico 5 today, you will have an opportunity to buy an update to Dorico 5 at a reduced price within the trial period.