P4v Integration error

I have created a new branch (N) from one of my code lines (A). Now I am trying to integrate some files from another codeline (B) having the same tree structure into my new branch.

I am using Integrate option from P4v GUI.Source branch is B and target branch N and using a branch spec to accomplish this.

While integrating I am in the workspace which has branch N in its view but branch B is not in view as it resides on another server.

I am continuously getting the following error Integration error - no target file(s) in branch view

I have searched on the net and seems a lot of people face this issue but haven't found any solutions. Please help.