Extensions Preferences is saying "Extension does not have permission to read, modify or transmit content from any webpages." but I've set SFSafariWebsiteAccess Level to All as per https://developer.apple.com/documentation/safariservices/safari_app_extensions/safari_app_extension_info_property_list_keys/adjusting_website_access_permissions. Any ideas about what might be wrong?
Can you please file a bug report using Apple's Feedback system and include your extension? it's hard to tell here without more information.
Please reply here with the feedback ID once you've done that.