Hi Ravi,
Just for documentation purposes, the way to solve the error message that you got was to maintain/assign the sales organization to the distribution channel. Then you assign or input them both when you create the article (I was trying to create a MC article and got the same issue as you did). I found the solution to solve this error and it was to go to SPRO -> Enterprise Structure -> Assignment -> Sales and Distribution -> Assign sales organization - distribution channel - site. Here I maintained the Sales Org. and DChCust/Mt (Distribution channel for customer and article masters). Upon saving, I can now proceed with creating the article (MC article in my case).
Regards,
Chester