Chris Quan
Ansys Employee
Are you using the External Gap for Lagrange/Lagrange Interaction?
If yes, can you click on Check to make sure the Gap size is appropriate? If the gap size is not appropriate, you need to change the gap size according to the instructions given by the program.
Also, check the Radius Cutoff in Controls -> Global Cutoff. Make sure SPH particle size is larger than the Radius Cutoff.