Sentinel isn't reading my heart rate

What this does

Sentinel reads your heart rate live during a session. When the number stays empty, the cause is almost always a permission that was declined once, a strap the app is refusing on purpose, or a device that needs your phone awake. Each has a different fix.

Before you start

Heart rate is captured by your phone, never by the web app and never by an iPad. The web app and iPad display what your phone collected and relay it, but they cannot read a sensor themselves. If you are looking at an empty heart-rate card on either of those, start your session on your phone.

A session is shared across your devices. Starting on one surface starts the monitoring on your phone, and stopping anywhere stops it everywhere. So an empty reading on the web usually means the phone side never got a sensor, not that the web lost it.

The five causes

1. A health permission was declined once

On iPhone and iPad, health access is asked for exactly once. If you declined it, iOS will not show that prompt again, and VEXA cannot re-ask. You have to turn it back on yourself in the iOS Settings app, under Privacy & Security, then Health, then VEXA AI.

On Android, health permissions are granted in the Health Connect app rather than inside VEXA. Health Connect needs Android 13 with the app installed, or Android 14 and later where it is built in.

2. Bluetooth was refused

If you deny Bluetooth, a Sentinel session does not start at all. That is deliberate: a session that silently ran with no heart rate would be worse than no session. If Sentinel refuses to start rather than starting empty, Bluetooth is your cause.

3. The strap lock

Once VEXA has paired a Bluetooth chest strap or band, it bonds to that specific device and refuses every other one. This stops it from grabbing a stranger’s strap in a gym. If you have changed straps, you must forget the old one first, using Pair a Different followed by Forget & Scan in the device setup sheet.

4. The device needs your phone unlocked

WHOOP and Fitbit Air stream over Bluetooth in a way that stops when the phone locks. For an uninterrupted session, set your phone’s auto-lock to never for the duration.

5. The baseline is still learning

A live reading that shows but reads “Collecting data” against the baseline is not a fault. Sentinel needs about twenty qualifying sessions before its baseline is calibrated, and it says so. It keeps working with safe starting thresholds in the meantime.

Steps

What you should see

A live beats-per-minute number that updates every few seconds, with BIO STRESS, SESSION AVG and a baseline reading beside it. During the first sessions the baseline reads “Collecting data”, which is expected.

Two things that are working as intended

• An Apple Watch session adds Exercise minutes to your Activity Rings. That is how Apple counts any workout session, and VEXA cannot suppress it. VEXA does not write a workout into Apple Health.
• Session average is computed on your device while the session runs. The server value only exists once the session has ended, so a mid-session number and an after-the-fact number can differ slightly.

If it doesn’t work

• Sentinel refuses to start. That is Bluetooth, not heart rate. Grant it and try again.
• The reading appears then goes to “Reconnecting”. Your strap has moved out of range or your phone locked. Bring them together and wake the screen.
• Everything is granted and it still reads nothing. Send support the device you are using, the platform, and the time the session ran. See Contact support.