If you're using Workbench Meshing you need a single multibody part coming from DM. Then check and (probably) delete all contacts in Meshing: there's a tolerance check which can cause false interface pairs.
You REALLY want to be using 2023R1 too. R17 is about 7-8 years old now and the technology has moved on a fair bit.
You are navigating away from the AIS Discovery experience