That is interesting because I have download the SE training guide and it opens fine in 14. The general rule is that the full versions (... 13,14,15) can open start edition files but the Start Edition version of the software cannot read full version files. There must be a glitch in your particular case.
Some things to think about: Are you using a full license, education license, trial etc.? When you download and install the training guide package I assume that you are opening the .pla files within the guide's folders, correct? Do you receive an error message from ArchiCAD when attempting to open the files?