Check the components that you use in Kodular and don’t exist in Niotron and remove them from the project before importing the aia to niotron, otherwise it won’t work.
If the component exist in both builders but have different name you can edit the .aia file and change component name and so it will work. There are tutorials about it in the internet, but basically you will have to edit the .scm and .bkm files to change the name of the component from the name used in Kodular to the name used in Niotron…
By the way, I made a guide a few days ago listing the components that Kodular has and niotron not and the other way around, may be it can help you too.
In the guide there is not a list of blocks present in each component, so even if the component exist in both builders it is possible that the .aia won’t perfectly work. If it is a small project it is easier to restart the project from scratch, specially if you will have to remove a component that is very used in your project in Kodular