When you try to open a template inside Premiere Pro or After Effects and get a 'damaged project' error message, it means you currently don't have the software version the template requires.
To find out which which version of the software you will need, go the template's product page, and check the version of the software under Item Details.
If you have an older version of the software, we suggest that you download the trial of the current version. This will be a fully functioning version of the software that you will be able to use for 30 days.
NOTE: If a template cites a specific software version like 2017.1 or 2015.2, then it means you will need to upgrade your software to that version, or a newer version, in order to be able to open the template.
For example, if you have Premiere Pro CC 2017 installed on your system, and the template requires 2017.1, you will not be able to open the template, because the 2017.1 version is higher than the 2017 version.