A voice message will not upload

Is the feature on

Voice messages are off until you turn them on, in Settings under Behaviour. If the record button is not on your pay card, that is why.

Is it under fifteen seconds

That is the limit. A longer recording is refused. The recorder stops on its own at the limit, but a file attached some other way will not be.

Which browser

Recording works in Chrome on Android and Safari on iPhone. Some browsers cannot record at all, and in those the option is simply not offered rather than offered and broken.

Did they allow the microphone

The browser asks once. If they said no, the button does nothing afterwards and there is no second prompt. They have to allow the microphone for kulhad.co in their browser settings and reload the page.

Are they on a slow connection

The recording uploads when they press I have paid. On a weak signal that can time out. Trying again on wifi usually works.

If the recording fails, does the payment fail too

No. The payment and the recording are separate. Somebody whose recording did not attach has still paid and their claim is still in your pending list, with whatever they typed instead.

If it keeps failing

Ask them to type instead, and write in with your page name and roughly when it happened.