I am getting the same error. Tried going to Freeway support. What a way to find out Softpress has gone under! I hope someone has an answer to this. Looking at other entries this seems to be a pretty common problem, but I don’t see a solution to any of the queries that I haven’t tried. I just had to erase and install the OS (10.11.5) and wonder if the problem is related to this.
I don’t think it has anything tp do with the Mac OS.
I was working on the same file but not on my Imac as usual but on my macbook. My home folder on the macbook had an other name than on the Imac. Now after changing the homefolder name, everything works fine again.