The boundary condition should be part of the flow region, not solid parts. In this case, make sure that those velocity inlets are part of the flow region (it can be done by moving the ground up to them, for example as in the example project it is shown).
Hi thank you so much for answering, I tried to rebuild my design and I found because I found a gap in my design. Here’s is the new link 11jan | SimScale Workbench
The boundary error is now fixed and I left with “A setup with at least 157 regions is being used in a single-region analysis type. Please delete CAD regions that are irrelevant for the simulation. If all CAD regions are relevant, ensure that only one region is assigned to the material and that all other bodies are assigned to advanced concepts” error.