Adobe Premiere Pro software should be able to help you with exporting CPA audio to MP4 format. Other than that, there is probably no way how to export CPA to MP4.
Convert Adobe Premiere conformed audio to MPEG-4 video file format.
We found 2 software records in the database related to .cpa to .mp4 file format conversion.
Microsoft Windows software - convert cpa to mp4 on Windows
A timeline-based video editing software from Adobe
Convert from cpa file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned cpa to mp4. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert cpa to mp4 on OS X
Mac version of Adobe's prime video editing software