Hi!
There’s an issue with the geometry. The rotating zone volume should be 100% solid and should intersect with the flow volume (think of the rotating zone volume as a plain, 100% solid part).
In your case, the “impellerdomain” and the “fluiddomain” have an interface between them (which shouldn’t happen, given that they should be fully intersecting with each other):
In your geometry, the blade walls are part of the “impellerdomain” but they should also be in the “fluiddomain”. Check this article for more insights: How to Prepare the CAD for Simulating Rotating Zones | SimScale
I took the geometry to Onshape and made some changes in it. Posting 2 pictures from it here to compare with the pictures from your geometry:
Feel free to use this geometry if you want. It should be good to go: https://www.simscale.com/workbench/?pid=3173767598368479589&mi=geometry%3A1&mt=GEOMETRY