Exactly. The problem is not related to Nuendo at all.
That warning dialog is a nuisance, for sure, but should not prevent you from running Nuendo.
It seems that a Soft-eLicenser has been created on your system, a Soft-eLicenser with a problematic serial number.
That is none of your fault, but a rare issue with the Soft-eLicenser.
There 's only one way to fix this problem: Deleting that Soft-eLicenser.
In case your Soft-eLicenser doesn’t contain any important licenses, you could delete the Soft-eLicenser without any harm.
In case your Soft-eLicenser does contain important licenses, please contact technical support, because after deleting your Soft-eLicenser, you will need to get replacement licenses.
Anyway, I would doubt that your Soft-eLicenser contains any important licenses, because it is difficult to download licenses into a Soft-eLicenser that exposes this kind of problem.
Why has a Soft-eLicenser been created on your system?
Most probably, you did install a software that requires the Soft-eLicenser in order to store a demo license within the Soft-eLicenser.
I would assume that, when viewing your Soft-eLicenser with eLCC, you’ll see a demo license of kind “local soft” that is stored within your Soft-eLicenser.
My advice would be:
Run eLCC and check the contents of your Soft-eLicenser. Most probably, the Soft-eLicenser contains some kind of demo license (of type “local soft” ).
If you can easily do without the Soft-eLicenser and its demo license(s), simply delete the Soft-eLicenser from your system.
To uninstall the Soft-eLicenser, please follow these steps:
Quit Nuendo, eLCC etc. Quit every application that is using the eLicenser(s).
Remove/rename the Soft-eLicenser content file which is located at: /Library/Application Support/Syncrosoft Soft-eLicenser/SeLicenser.sel
Launch eLCC to verify that the Soft-eLicenser is gone.
Launch Nuendo to verify that the issue was solved.
As Martin pointed out, it is possible to automagically delete the Soft-eLicenser and create a new (empty) one using the helper tool: