*** ERROR # 2922 *** Residual structure should be empty while using ASSIGN,MBDINP. I'm getting this error. Kindly let me know what can be the exact problem with my model?

It sounds like you're working with flex bodies. Here are some basics for flex bodies:

https://2019.help.altair.com/2019/os/topics/solvers/os/flexible_body_generation_intro_r.htm

If this doesn't help, feel free to reach out to support for Motionsolve/Optistruct. hwsupport@altair.com

Hi Nick,

Thanks for the support. Will check and come back if it doesn't work.