So this is happened before, but my soft elicenser got deactivated. I ran the reinstaller. Tried to recreate the Soft-eLicenser on my computer, but this is coming up everytime! Have tried to troubleshoot- I need Dorico 3.5 NOW for work!
This looks like the file SYNSOACC.dll is still active and therefore locked for overwriting.
One way to get rid of it is simply a reboot of the machine.
Another way is to open the Task Manager in Windows and look for everything that is from Steinberg, then kill those processes. One of them is probably the Licensing Engine, SYNSOACC.dll is part of it.