Dera Kumar

In Autodyn, considering an initial gap between different part is very important. It seems one of your gaps is less than minimum required. I suggest you to model again all of your parts with higher gaps. Good lock

Amir 

Aswani Kumar Bandaru

1. In the interaction, tab go to the create option and select TRM_SRF to create the minimum required calculated gap in the external gap method.

2. Else manually translate the part using the minimum gap (suppose 0.01mm) in the normal direction.

Either of these will solve the problem.