Compressor/decompressor(codec) not installed

[Ermananda]

I just upgraded from premier elements 12 to 15.  Now my video projects prepared in PRE 12 will not play.  I get the message "compressor/decompressor(codec) not installed.  How can I fix this.  I am using the same computer (Windows 10) and when I open the old PRE 12 program the projects still run perfectly.

[Steve Grisetti]

You will not be able to open a project created in version 12 with version 15 of the program. In fact, as I indicate in my book, it often corrupts the project file so badly that you can't open the file afterward in either program.

Complete any project in the version of the program that the project that was created in. Although some recent versions of the program can open almost recent version projects, the program should not be considered backward compatible.