Cannot upload a publication to yudu.com since I upgraded to El Capitan

Since upgrading to El Capitan from Mountain Lion, I have not been able to upload a publication to my Library on free.yudu.com. I had no problems before. Other web pages work fine.

I tried uploading a file that I had previously uploaded with no problem and when it gets to 100% it goes to the yudu home page instead of to the item page to view it. It just disappears.

I have the current Flash version and have tried both Safari 9 and Firefox 43.

Yudu tech support thinks it is a problem with flash and El Capitan. I use the flash uploader that yudu has on their site.

Any ideas? Thanks