@rockthedragon
I can’t find a changelog for your theme. I note that your theme vendor does not currently offer your theme for sale. Does that mean its no longer supported? Consider contacting your theme vendor to ask if you have the latest version of your theme and whether its compatible with the latest version of WC which you have: 2.4.13. They may be able to help with the cart problem.
@eugeniostepline
I can’t tell whether updating the parent theme will fix the problem. As you’ve already got another setup with this version then maybe that’s not the answer. However, the changelog does show lots of WooCommerce changes between 3.3.1 and 3.9.1, so updating the parent seems a reasonable way forward.
I can’t tell whether your developer made changes to the parent theme. Hopefully your developer did not do so. Any such changes will be lost by an update. Updating should not affect a child theme.
Updating can bring its own problems but probably less so than staying with an outdated version.
WordPress and WooCommerce try to be backwards compatible but 100% compatibility with older software is not realistic. Other theme authors have been bringing out updates in recent months to sync with developments in WP & WC. I think for WooCommerce compatible themes it would be normal for there to have been an update in the last three months or so.
A “theme update available” notification in admin is common but by no means universal.
You should look at your theme documentation or contact your theme vendor to find out the theme update procedure.
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