Cannot use different purchase class for I and N types

unknown

Hello Team,

Please help me with the below issue. 

We have recently reviewed and changed our Purchasing and Inventory classes in IC11, since then we have been seeing " Cannot use different purchase class for I and N types" error while creating purchase orders. I have cross checked the Purchasing and Inventory class they are same (No Spelling Mistakes or Other issues) 

Thank you in Advance. 

unknown

Sounds like something isn't clearing out correctly. If it's pulling in information from the line before, etc? When it occurs, if you ctrl+shift+k or shift+f3 or whatever clears the screen and try - what does it do?