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Sobre el error Falta el campo «mainEntity» con yoast seo

He estado revisando la documentación de apoyo de google para el marcado schema de FAQ o frequently asked questions y parece que Yoast está poniendo mal el schema, o es que no lo habéis cubierto bien.

Cuando creamos un schema de FAQ con un plugin, lo que se hace es poner un código J-son en el Head de la URL, en el caso del schema FAQ tiene esta pinta:

<script type="application/ld+json">
    {
      "@context": "https://schema.org",
      "@type": "FAQPage",
      "mainEntity": [{
        "@type": "Question",
        "name": "What is the return policy?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "<p>Most unopened items in new condition and returned within <strong>90 days</strong> will receive a refund or exchange. Some items have a modified return policy noted on the receipt or packing slip. Items that are opened or damaged or do not have a receipt may be denied a refund or exchange. Items purchased online or in-store may be returned to any store.</p><p>Online purchases may be returned via a major parcel carrier. <a href=http://example.com/returns> Click here </a> to initiate a return.</p>"
        }
      }, {
        "@type": "Question",
        "name": "How long does it take to process a refund?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "We will reimburse you for returned items in the same way you paid for them. For example, any amounts deducted from a gift card will be credited back to a gift card. For returns by mail, once we receive your return, we will process it within 4–5 business days. It may take up to 7 days after we process the return to reflect in your account, depending on your financial institution's processing time."
        }
      }, {
        "@type": "Question",
        "name": "What is the policy for late/non-delivery of items ordered online?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "<p>Our local teams work diligently to make sure that your order arrives on time, within our normaldelivery hours of 9AM to 8PM in the recipient's time zone. During  busy holiday periods like Christmas, Valentine's and Mother's Day, we may extend our delivery hours before 9AM and after 8PM to ensure that all gifts are delivered on time. If for any reason your gift does not arrive on time, our dedicated Customer Service agents will do everything they can to help successfully resolve your issue.</p><p><a href=https://example.com/orders/>Click here</a> to complete the form with your order-related question(s).</p>"
        }
        }]
    }
    </script>

No te asustes por el código, solo fíjate que todas las preguntas del FAQ van dentro de un campo que dice:
«mainEntity»: [{
-> aquí van las preguntas
y se cierra con }]

Pues parece que Yoast o algo hace que no se escriban bien las preguntas en el este código.

Yo os he dicho mil veces que prefiero antes Rank Math porque el schema lo trae gratis de base y suele estar bien, pero bueno, si no queréis cambiar a rank math simplemente crear el schema en el Schema markup generator y lo metéis en el head de la URL que os interese usando un plugin de añadir código en el head o el módulo elements de GeneratePress

Un saludo!