Ivy,
Thanks for the idea. I took another look at the file path. First I made the file names simpler to see if that was the problem. The downloaded file was then 4kB instead of the 22MB but more than 0kB as before. I then used the full link instead starting from starting from http://capturingchinese.com/.
This results in the following error:
Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 18353907 bytes) in 
Hosting4445488htmlwp-contentpluginswp-cart-for-digital-productsdownload.php on line 114
I’m now more confused than before.
Any help is appreciated.
Cheers,
Kevin