Greetings Kamran, I spoke with you a few moments ago about a process workflow in Salesforce, and utilizing the checkbox things work fine at first, but then flow fails to execute soon after and opportunities will not post. Here is the message. This was built using our Process Builder. Hope it helps.

Encountered unhandled fault when running process Add_Opportunity_Contact/301G00000000Hyk exception by user/organization: 005G00000045Dmu/00DG0000000lK3t

caused by element : FlowDecision.myDecision
caused by: The flow failed to access the value formyVariable_current.CnP_PaaS__CnP_OrderNumber__r.Cn P_PaaS__Contact__r.Id because it hasn't been set or assigned.