Connecting Multiple Raspberry Pis to a Cloud Mirror

The primary role for my Cloud Mirror is backing up my Windows Systems, but I would also like to use it to back up some environmental monitoring data from a couple of Raspberry Pis. Following ‘recipes’ from various places on the internet, I enabled SSH on the Mirror and was able to map a mount point on one of my Pis to a Share on the Mirror - that connection remains open and seems to be working fine. However, attempting to do exactly the same thing (mapping to a different Share) from another PI fails with a very unhelpful error message (“mount error(22): Invalid argument”). Is it really not possible to maintain more than one simultaneous connection with a non-Windows system, or am I missing something?