When trying to open .camrec or .camproj files in Camtasia 2020 or later I am unable to view the files or nothing happens.
Camtasia 2020 and later has retired support for both .camrec recordings and .camproj files as .tscproj and .trec files have been the default format since version 9 was released. These files will need to be opened in an earlier version of Camtasia such as version 9, 2018, or 2019.
These versions can be downloaded here and your software key for version 2020 or later will unlock these older versions.
The .camproj project files can be updated to a .tscproj file by simply opening this in version 9, 2018, or 2019 and selecting File > Save As... and this new .tscproj file can be opened in version 2020 or later.
The .camrec files cannot be converted to .trec files to be used in version 2020, so you will either need to edit these in an older version of Camtasia, or produce this as an mp4 from an older version of Camtasia, and import the resulting mp4 into Camtasia 2020 or later.