THIS PROJECT CANNOT BE OPENED IN THE STUDIO EDITION YOU ARE USING. ONLY PROJECT PACKAGES OR SINGLE DOCUMENTS CAN BE OPENED. This error message suddenly started appearing on trying to open project files which had previously (we're talking a matter of hours) been working fine. I have tried installing Studio 2019, parallels, even using a different laptop to no avail. The tech guy for the translation agency was also at a loss. I am not particularly techy, so if anyone can help it would be much appreciated, and if answers can be not too technical.
Thanks in advance!