Endpoints that require certificates

Hi all,

I am trying to use the join snap with 3 inputs. The solution works when I use two joins after each other but now I wanne try if it's possible to use only one join with three inputs.
I always get the error: failure: Right join path not found for input2, Reason: Right join path is required, Resolution: Please address the reported issue.

But the mapping is looking right to me.

My three inputs:

Pipeline in the attachment with the dummy data (change the extension from .json to .slp and upload it into your designer)