Only log that comes out is:
Adding feed (#45 - Campaign Monitor Feed 27) for entry #1864 for gravityformscampaignmonitor to the processing queue.
The campaign monitor plugin still worked before December 20, 2023, after which the update (4.0.0) was performed in which a queue was added. Unfortunately, I cannot find this in the database or whether it is stored.
We’ve responded to your support ticket about this issue:
To trigger the processing of background tasks, such as queued feeds, the plugin uses the wp_remote_post function to send a request to your site’s Ajax endpoint (/wp-admin/admin-ajax.php).
Here’s the important line from the system report:
Background tasks: No ✘ Reactiecode: 403
This indicates requests to your site’s Ajax endpoint are being blocked by a 403 forbidden error. This could be from the security module on the server hosting the site, or it could be from the theme or another plugin.
Have you tried running through a full conflict test: Testing Theme/Plugin Conflict
Note that for a valid conflict test, the first test must be done with only Gravity Forms & Campaign Monitor enabled. All other plugins should be disabled, and a default WordPress theme without custom code should be used (e.g. Twenty Twenty-One).
If you don’t feel comfortable doing this on the live site, try creating a staging clone or sandbox setup for testing.
If the issue remains when only Gravity Forms and Campaign Monitor are enabled, that would suggest the error is from the security module on the server hosting the site, at which point you’ll need to contact your web host for support.
A deny was set to the IP address on the server, so that no background tasks were performed.