I’ve just been trying some of my files, I have misunderstood the error messages. Basically I can still open files from versions 11.5 and newer, but I cannot open files made in r11 and older. A lot of my earlier stuff was made in r11 and trying to open these files is what failed and sent me down this rabbit hole.
Most of the projects I want access to were made in r16, so it’s not as bad as I thought. I asked Maxon about accessing r19 if I paid for a full licence and they’ve suggested they could help me out. I’m probably not going to do that, but I’m impressed with their service desk’s response.