Victron fix · Cerbo GX & VRM
Cerbo GX not connecting to VRM? Diagnose it in order
A Cerbo GX that won’t report to the VRM portal is nearly always one of six causes, and they’re quick to tell apart if you check them in the right order. Here’s the ladder we use on our own van — which runs VRM over mobile broadband from a moving vehicle, so we’ve met most of these in the wild. Rated 4.9 on Google.
- ● Six causes, in order
- ● Error #150 explained
- ● Works on 4G/5G & Starlink
First split
Is it the internet, or is it VRM?
Everything follows from one distinction: a Cerbo with no internet and a Cerbo with internet that can’t reach VRM look identical on the portal (“last seen 3 hours ago”) but have completely different fixes.
On the device or Remote Console, open Settings → VRM online portal. A recent “last contact” means the link is fine. An error there sends you to Settings → Ethernet / WiFi: no IP address or gateway means it’s a plain networking problem (steps 2–4 below); a healthy IP with a VRM error means something between you and Victron’s servers is in the way (step 5).
The classics
The two hardware traps everyone hits once
- The power-only USB port. The USB socket next to the HDMI output supplies power and nothing else. A WiFi dongle in it lights up and does nothing — the single most anticlimactic fault in the Victron world. Move it along one port.
- 2.4 GHz WiFi only. The Cerbo cannot see 5 GHz-only networks. Phone hotspots are the usual culprit — recent iPhones hide the 2.4 GHz band unless “Maximise Compatibility” is on.
Error #150
What error #150 actually tells you
The dreaded “connect error #150” means: I have a network, but I can’t reach VRM’s servers. The Cerbo needs outbound HTTPS (port 443) and working DNS — nothing inbound, no port forwarding, ever. So #150 is nearly always the network being selective: guest WiFi blocking unfamiliar devices, a firewall allowing browsers but not machines, a captive portal waiting for a login the Cerbo can’t give, or broken DNS.
The fastest proof is a network swap: hotspot the Cerbo from your phone for five minutes. If VRM springs to life, the device was never the problem — the original network was.
Good news
Mobile broadband, CGNAT and Starlink all work
Worried that 4G/5G routers or Starlink can’t run VRM because they use carrier-grade NAT and you can’t port-forward? You don’t need to. The Cerbo only ever dials out, so VRM works behind CGNAT without any configuration at all — our own van reports to VRM over a Three UK mobile connection from behind CGNAT, every day, while driving.
Data gaps heal themselves too: the GX buffers its logs while offline and uploads the backlog when the connection returns, so a signal blackspot costs you nothing but the delay.
Still stuck
Firmware, the new UI, and when it isn’t you
- Update Venus OS (Settings → Firmware) and reboot — VRM connectivity fixes appear in release notes regularly, and a reboot after an update clears more of these than anyone likes to admit.
- Realtime vs reporting: the portal’s realtime view is a separate two-way link — some users with the new GX interface have seen it decline realtime under load while scheduled reporting carries on fine. If “last contact” updates but realtime won’t open, that’s your shape.
- Check it isn’t Victron: genuine VRM outages happen rarely; when the community threads light up with the same symptom at the same minute, put the settings down and wait.
Independent guide: 365 Techies is not affiliated with, endorsed by or authorised by Victron Energy B.V. or Nabu Casa, Inc. Home Assistant is a trademark of Nabu Casa; Victron Energy is a trademark of Victron Energy B.V. Our dashboard work is listed on Victron’s Recommended Software Integrator programme — the opinions and measurements here are our own, from our own installation.
// RELATED
VRM healthy and hungry for more? Put the whole system in Home Assistant with the official integration, see the custom VRM dashboards we build worldwide, our South Coast Victron installs, or ask us directly.
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// GOOD QUESTIONS
Frequently asked
What does Cerbo GX error #150 mean?
It means the Cerbo has a working network but cannot reach the VRM servers — usually blocked outbound HTTPS (port 443), broken DNS, or a captive-portal login page it can never complete. Prove it with a network swap: hotspot the Cerbo from your phone, and if VRM comes alive the original network was the blocker.
Do I need port forwarding for VRM?
No, never. The GX device only makes outbound connections, so VRM works behind any router, carrier-grade NAT, 4G/5G mobile broadband and Starlink with zero configuration. If a guide tells you to port-forward for VRM, it’s wrong.
Will VRM work on a 4G/5G router or Starlink in a van or boat?
Yes — outbound-only traffic means CGNAT doesn’t matter. Our own campervan reports to VRM over a Three UK mobile connection from behind CGNAT every day. What does break VRM on the road is captive-portal WiFi at campsites and marinas, which is a reason to prefer your own mobile router.
Is my history lost while the Cerbo was offline?
No. The GX buffers its log data locally while disconnected and uploads the backlog once VRM is reachable again, so gaps backfill themselves. Only the realtime view is genuinely live-or-nothing.
The Cerbo shows online but VRM realtime won’t load — why?
Reporting and realtime are different links: logging is a periodic outbound upload, realtime is a persistent two-way session. If "last contact" stays fresh but realtime fails, look at two-way communication being disabled in Settings > VRM online portal, a network that kills long-lived connections, or the device declining realtime under load on the new interface.
Can you just fix it for me?
Usually, yes — most VRM connection problems are diagnosable remotely from what the VRM portal menu shows and a description of the network. We support Victron monitoring for customers worldwide and we’ll tell you straight if yours is the rare one that needs hands on the hardware.
Still not reporting?
Send us what the VRM portal menu shows and where it’s installed — van, boat or building — and we’ll tell you honestly what we’d check next. We support Victron monitoring remotely for customers worldwide, and if the fix needs hands on the kit we’ll say so rather than guess.
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