Owin HostService throwing exception "Could not load file or assembly"

Hi guys.

I am trying to get the Owin HostService to launch an app locally. The application works fine in IIS. I am using the Chrome version.
Once I run the Wisej.Application.exe, I get the exception about one of the DLLs we use, it is a third-party framework DLL:

Could not load file or assembly ‘XXXXXXXX’ or one of its dependencies. An attempt was made to load a program with an incorrect format.

All dependencies seem to be there and is working fine when accessing through any browser to the deployed server.
Any ideas of what I should check?

Thanks in advance.

Ivan
(Wisej 2.2.46.0 – VS 2019 – C#)