CRP20101

El valor del campo TipoDeComprobante debe ser "P".

In English A CFDI with the Pagos complement must be a payment receipt: TipoDeComprobante P.

error: the document is invalid

What the rule checks

As the rule set's publisher wrote it. The rule runs on every element the context matches, and fails where the test is false; the validator reports the line of that element.

Context
/cfdi:Comprobante[@TipoDeComprobante = 'P' or cfdi:Complemento/pago20:Pagos]
Test
@TipoDeComprobante = 'P'

Checked with CFDI 4.0