Well, they moved to the new system in 2022. At the start of 2025, they will turn off the servers on the old system that you’re currently using. While Dorico should still work with your current dongle, if anything goes wrong or changes, then you might not be able to use Dorico.
Basically, you need to upgrade to Dorico 5. You can’t use the new system on D3.5.
The FAQ is here:
There are a great many engraving improvements and new features in the Dorico versions since 3.5. Some parts of the interface have changed (mostly concerning playback), but otherwise you’ll find it very familiar – and hopefully with fewer foibles!