I experience two issues updating from a WordPress site using Woopress with WooCommerce 2.6 to 3.1.
I updated the WooCommerce plugin and then uploaded the WooPress 3.1 version.
First, the gallery broke, as it was no longer recognizing the product image. When I tried to update the gallery on the product page the ‘add image’ button was no longer working.
Second, when a product has several attributes with wide variations, after selecting it either comes back with sorry out of stock message or going into a permanent spin of the blue preloader and never settles. This problem already started in the last few days on 2.6 , and was one of the reasons I wanted to update WooCommerce, however after the update it became a lot worse.So for instance if a shoe comes with several sizes and colours, it may only allow for several sizes but not others, or not at all.
I had to revert back to 2.6 version, but needs to resolve these issues.
Site URL: hidden Theme version: 2..6 WooCommerce version: 2.6.14
Please try this way of theme update: export theme settings in Theme Options > Import/Export > Import or Export your theme configuration > Export Options, then activate default theme (Storefront), rename woopress folder via FTP and upload new theme archive in wp-admin > themes or theme folder via FTP (without overwriting), enter your purchase code to activate the theme and skip Setup Wizard, then import your theme options. Check your site, if all is well, you can delete the old theme. Likely, after the update, you need to re-add widgets (Appearance > Widgets). Don’t forget to create backup of your files and database before starting update process!
Also, update all required plugins https://www.8theme.com/download-plugins/