I have the same problem :-/
Me too, but only with some products and I don’t know why 🙁
Was since I update Woocommerce to 3.0.6
I was trying changing protuct settings but I can’t resolve this.
I solve my problem!!!!!!
My problem was when Downgrade woocomerce from 3.0 to 2.6 now we aren’t able to save any changes to excisting products. We can make the changes but the button doesn’t do anything.
Solution: Its simple. 1. Just edit your Product. 2. Tick on DOWNLOADABLE (where we give price for products) 3. make value 0 where its -1 in Download limit and download expiry box. 4. uncheck again downloadable (if product is not downlaodable) Click Update button.
Thanks http://stackoverflow.com/questions/43756179/cant-update-products-in-woocommerce
Thank you lauradiaz. You saved my day 🙂