Troubleshooting¶

The connection dialog¶

"Chrome browser required"¶

The browser has no Web Serial or Web Bluetooth. Safari and Firefox do not implement them, and no browser on iOS or iPadOS does.

Use Chrome, Edge or another Chromium browser on Windows, macOS or Linux. See Browser support.

"Bluetooth is off"¶

The browser can see a Bluetooth adapter but it is disabled. Switch it on in the operating system; the tile goes live on its own, no reload needed.

"Connection cancelled or failed. Please try again."¶

Usually the browser's port chooser was dismissed. Occasionally the port was taken by something else — a serial monitor, an IDE, a previous tab of the Lab still holding it. Close the other user of the port and reconnect.

The port chooser is empty¶

The Lab only offers ports belonging to the controller board's USB chip. An empty list means:

the board is not powered, or the power supply is not switched on;
the cable is charge-only — a surprising number are;
the USB-serial driver has not loaded. Unplug, replug, watch whether the operating system reacts at all.

"At least one motor must be connected to continue."¶

No motor answered on any ID. Check, in this order: the power supply, the cable from the board to motor 1, then each link in the daisy chain.

"Motors with incorrect IDs detected."¶

Two or more devices are answering on the same ID, or a motor is on an ID outside 1–6. This is the normal state of a freshly built arm, because servos ship with the same ID.

Fix it with the Set motor IDs tool, or redo the ID step in Module 1: connect one motor at a time and give it its number. With more than one attached the app cannot tell them apart and says so.

"Motor speed is still limited from a previous emergency stop."¶

Exactly what it says. An emergency stop clamps the speed and the state lives in the servos, not in the browser.

Power the arm off and on, reload the page, connect again. Reloading alone is not enough.

A motor shows "Not connected"¶

Nothing answered on that ID. The bus is a chain, so a break shows up as that motor and everything after it going quiet. Reseat the cable at the joint before the first silent motor.

A motor shows "Not configured"¶

Something answered, but wrongly — two devices replying at once, or a reply from a different ID than the one asked. Treat it as an ID clash and use Set motor IDs.

While working¶

The 3D twin does not follow the real arm¶

Stop and fix this before doing anything else.

Is the arm actually connected? Check the sidebar.
Did the motor probe report six OK? Reconnect and read the table.
Are the IDs in the right order along the chain? A joint wired to the wrong ID moves the wrong limb on screen.
Has the arm been calibrated in this account? See Calibration.

The angles are wrong by a constant amount¶

The zero positions were captured in a pose that was not quite HOME. Redo the Module 3 calibration, taking more care over the pose.

The error grows the further the arm reaches¶

Range-of-motion calibration, or mechanics. Run the Calibrate robot tool; if it persists, check for a loose servo horn or a link that is not fully seated.

The emergency-stop dialog will not go away¶

It is a hard block by design: power the robot off and on, then reload the app.

"Camera unavailable — check browser permissions or switch back to the virtual camera."¶

The browser refused the webcam, or another application holds it. Check the camera permission for the site, close anything else using the camera, and reload. Both vision modules also run against the built-in virtual scene, so a broken webcam never blocks the course.

Remote sessions¶

"Connection failed. Check the code and try again."¶

The code is wrong, or the owner's session is not running. Codes are six characters and belong to the owner's account.

"Remote connection is not available — this tool requires a direct USB or Bluetooth connection."¶

Some tools talk to the bus directly and cannot work over a remote session. Connect the arm to this computer instead.

Remote sessions need an account on both ends.

The session never connects, with no error¶

Almost always the network. The connection is peer-to-peer through a public STUN server with no relay, and a restrictive firewall — school, university, corporate — can prevent it forming. Try a different network, or a phone hotspot, to confirm before blaming the app.

Account and access¶

It expires ten minutes after it is sent. Request a new one. Open it on the computer you intend to work on, in Chrome — not inside another app's browser.

A lesson sends me to the plans page¶

The lesson is behind the subscription. Module 0 and the dashboard stay open.

The certificate button is not there¶

It needs the first seven modules complete and an active subscription. See Progress and your certificate.

Still stuck¶

Use Send feedback inside the Lab — it can attach a screenshot, which usually saves a round trip — or write to hello@robonine.com. Say which module, which step, which browser, and whether the arm is on USB, Bluetooth or virtual.