Stopped working a few days ago

This plugin was working fine but a few days ago (maybe 3), the button disappeared from the sidebar. I checked the plugin and it is active. For some reason the check had disappeared in the settings for where the button is to appear: post or page. I rechecked it for Page and saved but it still doesn’t work. No button. What shows where the button used to be is [rps-paypal]

https://www.ads-software.com/extend/plugins/easy-paypal-custom-fields/