I did not have enough time to wait for this to be resolved unfortunately. I needed to get things working again quickly, so I went back to the earlier version of the site, that doesn’t use the “basic” plugin, and uses an older version of wordpress. And I made my other updates on that version of the site. I guess I will continue using that version of the site for a while.
I deactivated all the other plugins, but the invoices still don’t show up.
By the way, I am using version 3.09.5 of the plugin. When I updated the plugin to 4.1.2, it broke the website. So I reverted back to this version. I see the plugin is only tested up to wordpress 4.4.2, so I downgraded my wordpress to that version to see if anything changes, but it didn’t.
