In general software companies do not put much effort in assuring that a certain version of their software can read files created by a future version. But reading files created by a previous version of the software is pretty normal. Prime is no exception to this.
In some cases software may be capable to write a file in/for a previous version. Prime does not have that capability. PTC seems to want their customers to always use the latest version of Prime.
If you want, you can install Prime7 (Express, you do not need a license) and read the file. If you install Prime 7 on the same computer where Prime6 is installed you can have them run side by side and copy equations over from 7 to 6 and then save the file in Prime6. See here.
BUT installing Prime7 (express) on the same computer where Prime6 (licensed) is installed may cause you to lose your ability to convert Mathcad (15 and before) files to Prime. If you have another PC, you can install Prime6 and 7 (both Express) and try that route safely.
Or you can attach the Prime7 file and I'll see what I can do...
Success!
Luc
