Hello Miroslav,
I am sorry about the issue.
Are you trying to import the IWZIP of this project, or are you opening it from the list of projects available?
Thank you.

Eric

Online translation:

Witaj Miroslav,
Przykro mi z powodu tego problemu.
Czy próbujesz zaimportować IWZIP tego projektu, czy otwierasz go z listy dostępnych projektów?
Dziękuję.

Eric

I open them from the list of available projects.

Hello Miroslav,
could you please provide me with a copy of the project folder, so that I can attempt to reproduce the issue and identify whether it is a localized issue with your computer, or something involving the project itself?
You can find the path the projects are stored at by checking the Preferences settings.
Please make a copy of the folder, archive it into .zip/.rar format and upload the file with https://www.swisstransfer.com/ or similar services, and provide a download link at support @ incomedia.eu (without the spaces).
Thank you.

Eric