Fixed: Please update to macOS 15.1 to solve the firewall and security issues.
macOS 15 Sequoia was launched on September 16, 2024 and included some breaking changes in the Sequoia firewall and security features. According to TechCrunch and The Register many apps were experiencing issues (such as security apps and apps that use networking).
Apple quickly released a patch (15.0.1) for macOS Sequoia which attempted to fix some of these issues, but some customers were still report problems related to network disconnects.
Apple later released a new minor update (15.1) which has been reported by some customers as fully resolving the firewall and security issues.
Now that Apple have fixed the macOS 15 Sequoia firewall and security features in their 15.1 update, you may be safe to upgrade to that version and it is likely that you will not encounter issues. However, the fix is new so if you want to be extra cautious, you could remain on macOS 14 Sonoma for the time being.
If you are already on macOS 15 Sequoia then please try updating your system to 15.1 or higher. The Sequoia firewall and security feature issues was less severe with 15.0.1 but has apparently been fully resolved in the later 15.1 minor update.
You may need to update your permissions in the Privacy & Security settings (note: there is a new permission requirement in Sequoia). To enable Synergy for local network access:
There is a bug in macOS 15 Sequoia where the local network access settings (in Privacy & Security) do not apply to updated app bundles, so you may need to toggle the Local Network setting off then back on again:
If this article didn't help, you can talk to someone on our support team (unless we sent you here, in which case please reply via the ticket you already have open).