Hi Katya,
Specific requirements for the .zip file are described here:
You also want to make sure that your resource files are at the root of your ZIP file, rather than included in a subfolder.
PennController tries to download the ZIP file in the background at the beginning of the experiment. As this is done automatically via javascript, it is different from a manual download of the ZIP file (hence the need to use the .htaccess method).
And it is also different from accessing non-zipped files, as PennController downloads the zip file into the client’s cache and unzips it there to access the resource files it contains.
You can open your browser’s javascript console and refresh the page to look for any CORS related error/warning message: if you see any, it means that something is not right with the .htaccess configuration.
Let me know if the problem persists.
Best,
Jeremy