Unable to instantiate managed plugin class

we have a customer that is getting the following error when launching our app.
Error happens during Boot-Up as soon as we try to instantiate the first Hydra Plugin.

Unable to instantiate managed plugin class “…”. Most likely the type is not declared as “public”, type or assembly are marked as ComVisible(False), or missing/incorrect license file is detected.

We have installed this same version on other PC’s and it works just fine. Problem affects only this one machine.

Customer is using Dutch Windows 10 x64 build 18362

Hydra version

Plugin type is declared as public and ComVisible(true).

The license file must be present, otherwise it would not work on other PC’s.

Any suggestions on how to troubleshoot this?

Thank you!


Given the app works on other hosts, the issue is definitely not caused by the app itself. Something is wrong with the environment.

The 1st step to check is if the .NET Framework is installed. If your plugin uses .NET 3.5 then please go to the Windows optional features and check if the .NET 3.5 is installed at all.