Originally Posted by mvs
The problem is that you cannot upload the module for X-Cart 5.3.6.x on X-Cart 5.4.0.x. And tar/tgz/tar.gz formats are acceptable.
That is not the problem. The module is manually uploaded to 5.4.x then converted to 5.4.x format. Tested and all works under 5.4.x. Then exported from 5.4.x to package and then trying to re-import back that very same package - error shows and the installation is not allowed. The cart will not even upload the module package due to "format not allowed" or something like this