Check out this thread they seem to have killed/locked from further comment:
THIS is the exact problem I am witnessing, and it is VERY distressing. It seems to revolve around when they changed the way you would populate the CSV file. I hace worked with the tech geeks now for a LONG time, no resolution. What I was able to load in 1 minute 26 seconds (200 products--NO IMAGES, NO VARIANTS), no will not even get recognized by their system as a valid file. For "paul" to recommend in that previous thread to communicate with them, is a slap in the face to us that know what we are doing. It is true....they had me check browser, different system, all updates, make sure "extensions" weren't getting in my way.....all a cover-up to their inability to admit they have a problem here.
They deal with me like I don't know what I am doing. I have ~50,000 SKU's to upload here....pretty pathetic I need to use their CSV limiting me to 200 at a time. And then when I got the CSV to work 1 1/2 weeks ago....set about setting up my son to start blowing out 200 product CSV's to upload, then all of a sudden, their system doesn't even acknowledge the file type.
So far I have gotten handed off from tech-to-tech....one girl seemed to be onto something, and she told me it would get escalated to someone...then I am contacted by some other tech the next day, and he wants me to go through the same BS I did countless other times.
GET WITH THE PROGRAM SQUARESPACE!!! I successfully load up 10,000 sku's via crazylister/ebay CSV file....and am also in the process of muscling my way through listing 1500 SKU's at a time with the walmart marketplace system. GET IT WORKING, AND GET IT WORKING NOW!