[Bug] Pushover notifications not working

Bug description Pushover notifications are never being sent.

Additional context The test notification (triggered manually in settings) does work so the credentials are properly configured and there is no firewall issue present either. The "Enable notifications for this subscription" option is enabled for all subscriptions. The "Default value from settings" (7 days) option is used as the "Notify me" option in the subscriptions' settings.

Affected version(s) Affects the latest version (4.5.0) but prior versions didn't work either.

Expected behavior Wallos should send Pushover notifications.