Live stream won't start: RTMP troubleshooting

You have set up live streaming, started your broadcaster, and... nothing. The gallery still shows "stream not active." This is almost always one of five problems, all fixable in under five minutes.

First thing: confirm where the problem is

Before diving in, figure out which stage is broken:

1. Is your broadcaster showing "Connected" or "Publishing"?
   • No → broadcaster can't reach Mux. See #1 below.
   • Yes → Mux is receiving. Skip to #2 below.
2. Does the viewer gallery show "Live"?
   • No, but broadcaster is publishing → the event's live config is off, or the Mux stream was disabled. See #3.
   • Yes → guests are watching. You're live, you're fine.

The five usual causes

1. Wrong RTMP URL or stream key

This is the most common failure. RTMP configs are fiddly and one character off silently fails.

Correct RTMP server URL: rtmps://global-live.mux.com:443/app

Note the s in rtmps, secure RTMP. Some older tutorials say rtmp:// without the s. That will not work on Mux.

Stream key is a long random string unique to your event. You can find it on the event page's Live Stream panel, click "Show stream key" to copy it fresh.

In your broadcaster:

• Larix Broadcaster: Settings → Connections → Add → Paste the URL and key into the two fields. Save.
• OBS: Settings → Stream → Service: Custom. Server: the RTMP URL. Stream key: the key.
• Streamlabs: Similar to OBS.

If you see "Failed to connect" or "Authentication failed" in the broadcaster, the key is wrong. Regenerate from the event page (Disable stream → Enable stream) and paste fresh.

2. Broadcaster is connected but gallery still shows offline

Symptoms: your broadcaster UI says "Publishing" or "Live" with a green indicator. The event gallery viewer shows "stream not active."

This is usually a 10-30 second delay between Mux receiving the stream and the viewer page detecting it. Wait a full 30 seconds. Then hit refresh on the viewer.

If it is still offline after 60+ seconds, one of these is happening:

• Mux stream got disabled. If you hit "End stream" or "Disable" on the event page, Mux stops accepting RTMP even though your broadcaster is still trying to publish. Re-enable the stream from the event page.
• The stream key was rotated. Same deal, if you regenerated a key but your broadcaster has the old one, Mux rejects the old key silently. Copy the new key into the broadcaster.
• Network is dropping packets. Your broadcaster thinks it is publishing but the stream is not actually arriving at Mux. Check your network, see #3 below.

3. Network problem on the venue WiFi

Weddings are notorious for terrible venue WiFi. RTMPS needs stable ~3-5 Mbps upload. Many venues give you ~1 Mbps download, let alone upload.

Signs of a network problem:

• Broadcaster UI shows "Reconnecting" or a red/yellow indicator
• Frame drops, dropped frames counter climbing fast
• Your own test clip from the same WiFi takes forever to upload in a browser

Fixes:

• Use cellular instead of venue WiFi. A 5G phone tethering with 2 bars beats most wedding venue WiFi for upload. Turn on Personal Hotspot on your phone, connect your streaming device to it.
• Move closer to the AP. Ask the venue tech for the main router location, set up nearby if possible.
• Drop your bitrate. In OBS/Larix settings, reduce video bitrate to 2000 kbps and audio to 128 kbps. Sacrifices some quality for stability.
• Change resolution. Stream at 720p instead of 1080p. Much more forgiving on flaky networks.

4. Broadcaster codec is not H.264

Mux requires H.264 video and AAC audio. Most broadcasters default to this, but some cameras and phone apps default to HEVC.

In OBS: Settings → Output → Advanced → Encoder must be x264 or an H.264 hardware encoder (NVENC H.264, QuickSync H.264, Apple H.264).

In Larix on iPhone: Settings → Video → Codec → H.264. Some Larix builds on newer iPhones default to HEVC, flip it.

If you are streaming from a GoPro or drone: check their app docs. GoPro Max and Hero8+ can do direct RTMPS but only in H.264 mode, not HEVC.

5. Firewall / corporate network

If you are at a corporate event or a venue with enterprise networking, outbound RTMPS on port 443 is sometimes blocked. RTMPS uses port 443 just like HTTPS, so this is unusual, but it does happen.

Test: from the same network, can you browse normal websites? If yes, port 443 is open for TCP but RTMPS requires a slightly different handshake. If no, the whole network is restricted.

Fixes:

• Use cellular / hotspot instead
• Ask venue IT to allow *.mux.com outbound
• Stream from a 5G phone + Larix, bypasses the venue WiFi entirely

Testing before the event

Always test end-to-end at least 24 hours before go-live:

1. Start the stream in your broadcaster at home
2. Open the guest gallery URL in another browser or another device
3. Verify you can see and hear yourself
4. Stop, start again, verify reconnection works
5. Ideally, test from the venue or a similar WiFi environment

Most disasters happen when the photographer tests for the first time 5 minutes before the ceremony starts. If something is wrong, you will not have time to fix it.

What if the stream keeps dropping mid-event

A stream that connects and then disconnects repeatedly is almost always network quality:

1. Switch to cellular hotspot immediately
2. If you cannot, drop bitrate aggressively (1500 kbps video, 96 kbps audio, 720p)
3. If you still cannot get it stable, accept that you will have a VOD recording after the event rather than a live broadcast. The VOD replay saves what was received.

What does NOT matter

Things people assume are the problem but rarely are:

• Time of day on Mux's side. Mux has 99.9%+ uptime. "Internet is slow" is almost always your side.
• Android vs iOS. Larix works identically on both. If Larix on iOS breaks but Larix on Android works, the difference is the cellular provider, not the OS.
• Your event tier. Pro is required to stream, but once enabled the stream itself is not plan-gated. A Pro stream and a Founding stream behave identically.

Still stuck?

After working through this list, if you are still offline:

1. Check status.mux.com for an active incident
2. Contact support with your event ID, the broadcaster app + version you are using, and what you see in the broadcaster UI (a screenshot helps)

If the event is starting imminently, include "event starts in X minutes" at the top of your message, we prioritize those.