Sampat Kumar
Ansys Employee

Hi Dusev,
Will you please use the material assignment option? Are you facing the same issue by right click on the material and selecting the material assignment option? if you still face this issue then select the None option in the mechanical view tab in the Engineering data. 
Click file --> options--> UI option--> Engineering data--> select None. 

Please let me know if you are able to assign the material or not.