Digital Product Download (Multiple files) not Working

Hello, I’m hoping someone can help me with an issue with digital product downloading not working please.

My best selling is a Calligraphy guide.The file size for the different modules is quite large so I have split this into 4 different zip downloads. I use Dropbox force download links to deliver the files (and enter the urls in the product page).

I deliver the downloads with dropbox on all my products, but the only one I have trouble is this one.

Every customer emails me after purchase to say they can’t download two of the zip files. It seemed to happen after the latest Woo Commerce update, so not sure if that’s connected. It starts to download, but then comes up with ’Network Error’.

I have tried rezipped and uploading, relinking and nothing seems to fix it.

Can anyone help please? Much appreciated!

Thanks,
Nicole.