SolarMark Blog · Troubleshooting

My inverter won't connect. Now what?

A troubleshooting checklist for local Modbus TCP monitoring.

August 24, 2026

Local monitoring has one moving part: the app talks to your inverter's IP address over your home network. That's it. So when a connection fails, the cause is almost always on a short list, and everything on that list is fixable. Work through it in order. It's sorted by how often each problem turns out to be the culprit.

Start with the built-in diagnostics

Before guessing, open SolarMark's connection diagnostics. It runs three checks in sequence, and the point of failure tells you where to look:

• Reachability fails. Your phone can't see the inverter's address at all. This is a network problem: wrong IP, wrong network, or the inverter is offline. Start at step 2 below.
• Port test fails. The inverter is there, but nothing is listening on the Modbus port. This is almost always step 1: Modbus isn't enabled, or it's running on a different port.
• Modbus handshake fails. The port is open but the conversation goes nowhere. Check the device type you selected, the unit ID, and whether another program is hogging the connection (step 4).

1. Modbus isn't actually enabled (the most common cause)

Every inverter brand ships with Modbus TCP switched off. Enabling it is a one-time change, but it has to happen before anything else works.

• SolarEdge: on inverters with no display, Modbus TCP is enabled through the SetApp installer tool (Site Communication, then Modbus TCP, then Enable). SetApp access is installer-only, so you may need to call your installer. The default port is 1502, not 502 like most brands, and entering the wrong one looks exactly like a dead inverter. More detail in the SolarEdge setup guide.
• Most other brands: the switch lives in the inverter's own menu, web interface, or installer app, and the default port is usually 502. The in-app setup guide has per-brand instructions.

If someone enabled it a while back, verify it's still on. Some firmware updates have been known to reset communication settings.

2. The inverter's IP address changed

Home routers hand out addresses on a lease. If you set up SolarMark with the inverter at one address and your router later assigned it a different one, the app is now knocking on the wrong door. There are two fixes, and you should do both:

1. Find the inverter's current address. Use SolarMark's network scan, or look in your router app under "Connected Devices."
2. Reserve the IP so it never changes again. In your router or internet provider's app (Xfinity, Cox, eero, etc.), find the inverter in the device list and choose "Reserve IP" or "Fixed IP." This ten-minute fix prevents the problem permanently.

3. Your phone and inverter aren't on the same network

The app needs to be on the same local network as the inverter. There are several easy ways to accidentally not be:

• Phone on cellular data instead of Wi-Fi. Local addresses aren't reachable from the cell network (unless you've set up remote access; see the remote monitoring guide in the app).
• Phone on a guest network. Guest Wi-Fi is usually isolated from your main network by design.
• A VPN running on your phone can route traffic away from your home network. Try toggling it off.
• Mesh systems with client isolation enabled will block devices from seeing each other even on the same Wi-Fi.

Quick test: can your phone open your router's admin page? If not, you're not really on the home network.

4. Something else is holding the connection

Some inverters, SolarEdge among them, accept only one Modbus TCP connection at a time. If a home automation system, energy logger, or another monitoring tool is already connected, the inverter will refuse or drop SolarMark's connection, and vice versa. If you run Home Assistant or similar, pause its integration for a minute and retry. If both tools need access long-term, increase the polling intervals so they aren't fighting over the line.

5. It worked before, but it's dark out

Some inverters shut down or stop responding when the sun goes down and there's nothing to produce. If your connection test is failing at 9 PM, try again in daylight before changing anything. On a related note: if the inverter connects by Wi-Fi from a far corner of the garage, a weak signal can cause intermittent dropouts that look random. A powerline adapter or an Ethernet run makes it rock-solid.

6. The long-tail causes

If you've cleared everything above and it still won't connect: double-check the unit/device ID (usually 1), confirm you picked the right device type when adding the inverter, and check whether your router's firewall or a "network protection" feature is blocking local traffic between devices.

Still stuck? Email us with the details

Send a note to support@solarmark.us with your inverter brand and model, how it's connected (Ethernet or Wi-Fi), what the diagnostics screen shows, and what you've already tried from this list. That's usually enough to pinpoint the problem in one reply.

And remember, this is exactly what the 14-day trial is for. Get the connection solid first, then decide.