When Screens Assist tries to automatically configure your router for remote access, it uses a feature called port mapping. Occasionally, errors may occur during this process. This article explains what these errors mean and how to fix them — no technical background required.
❓ An unknown error occurred
Message: An unknown error occurred.
This is a general error that can happen when something unexpected gets in the way of setting up your connection. If you see this repeatedly, try restarting your router and Mac. If the issue continues, contact us and we’ll help you investigate.
⚙️ An invalid value was provided
Message: An invalid value was provided.
This usually points to a technical issue in the configuration. It’s not something you caused. Try restarting the app or your Mac. If you still see this, get in touch with us.
🌐 NAT traversal is not currently available on your network
Message: NAT traversal is not currently available on your network.
Your network doesn’t currently support automatic port configuration. This can happen on guest Wi-Fi, public networks, or when certain security settings are enabled. Try switching to your main home Wi-Fi, or check your router settings if you have access.
🔥 A firewall is blocking the port mapping request
Message: A firewall is blocking the port mapping request.
Your Mac’s firewall or router firewall is preventing Screens Assist from setting up access. To fix this:
- Open System Settings > Network > Firewall and make sure it’s either turned off or allows Screens Assist.
- Some routers also have their own firewalls — if you’re comfortable, log in to your router and check its security settings.
⚠️ Your system is incompatible with the Bonjour service
Message: Your system is incompatible with the Bonjour service.
This means something on your Mac is interfering with Apple's Bonjour service, which Screens Assist uses to communicate with your router. Restart your Mac and make sure no apps are blocking system network services.
🚫 This operation is invalid
Message: This operation is invalid.
This error may occur if something on the system changed unexpectedly (like the network disconnecting during setup). Try restarting the app and ensuring you're connected to the internet.
🌐 Double NAT detected. Port mapping may not work correctly.
Message: Double NAT detected. Port mapping may not work correctly.
Your internet setup may have two routers (for example, a modem/router combo from your ISP and your own Wi-Fi router). This can confuse Screens Assist. To fix:
- Try enabling bridge mode on one of the routers.
- Contact your internet provider if you’re unsure how your network is set up.
🧩 Bonjour or a required service is not running
Message: Bonjour or a required service is not running.
Bonjour is a built-in macOS service used by Screens Assist. Restart your Mac to restart Bonjour. If the issue continues, check if you have apps or security tools that might be disabling macOS network services.
📡 Your router does not support NAT port mapping
Message: Your router does not support NAT port mapping.
Some routers — especially older models or mobile/5G hotspot-style modems — don’t support automatic port configuration using NAT-PMP or UPnP. Without this support, Screens Assist can’t open the necessary port to make your computer accessible remotely.
To address this:
- Log into your router or modem settings and check if UPnP or NAT-PMP can be enabled.
If you're using a mobile hotspot or cellular router (on a 4G or 5G network), port forwarding is usually not available at all. This is due to restrictions by mobile internet providers, who often block incoming connections for security or technical reasons.
In these cases, remote access through Screens Assist won’t be possible. For best results, we recommend using a standard home or office network with a compatible Wi-Fi router.
🚫 NAT port mapping is disabled on your router
Message: NAT port mapping is disabled on your router.
Your router supports port mapping, but the feature is turned off. To fix:
- Log in to your router’s settings
- Look for UPnP or NAT-PMP
- Turn it on
If you’re unsure how to access your router, check the underside of the device or your ISP's documentation.
❌ No router was found on your network
Message: No router was found on your network.
Your Mac isn’t connected to a network that provides internet access. Check that you're connected to Wi-Fi or Ethernet, and make sure your internet is working.
🕗 Polling mode is active, which prevents port mapping
Message: Polling mode is active, which prevents port mapping.
Your system is using a network mode that disables automatic configuration. This may be due to enterprise policies or older system configurations. If you’re on a home network and seeing this, restart your Mac or contact support.
⏱ The operation timed out before it could complete
Message: The operation timed out before it could complete.
Screens Assist tried to contact your router, but didn’t get a response in time. This can happen on unstable or slow networks. Try again after a moment, or restart your router.
Still stuck?
If you're not sure what to do, feel free to contact our support team. We’re happy to walk you through it — even if you’re not tech-savvy.