đź’ˇ There is no "universal key" for MPEG-4 in version 15 because the keys are uniquely tied to your specific Passport ID . Your best options are to patch the software to the latest version or transcode your video files to a compatible format using free tools.
To understand the "MPEG-4 key," one must understand how Pinnacle structured their software in the early 2010s. Pinnacle Studio was sold in tiers:
Pinnacle Studio 15 was released in 2011 and is now considered a product. Because the original activation servers for this version are no longer maintained by Corel (the current owner of Pinnacle), standard automated activation for the MPEG-4 codec is generally no longer possible. ⚠️ Important Status Update