My guess is there is a plugin conflict that is causing that fatal error. The message you shared references a plugin called woo-invoice. So, you may try to disable that particular plugin and see if that stops the fatal error from happening again.
If the issue keeps popping up, you’ll want to run a full conflict test:
1. Switch the theme of your website to the free Storefront theme.
2. Deactivate all the plugins except for WooCommerce and check if the issue persists. If the problem is resolved then please move on to the next step.
3. Activate features one by one while testing for the issue, until you find the one that is causing this behavior.
We recommend that these steps are taken on a staging site, which is a clone of your live site that you can modify without risking making any permanent damage to your live site. You can create it using a plugin like WP-Staging. This plugin lets you copy and redeploy a WordPress site with minimal work.
