Cannot open Swift Publisher documents

I upgraded to High Sierra this evening. While this has gone smoothly and there appears to be a speed increase in many applications there is a major problem with Swift Publisher 5. While the application opens as expected it is unable to open any existng files or create any new ones. It appears that the new file format is not compatible with Swift Publisher. Strangely an old version of Printworks seems unaffected.

Any suggestions peeps?

Computer is a 2014 MacBook Pro with 16GB and i7 processor.