Why am I getting: AskSdk.Request verification failed Error, Missing Certificate for the skill request?

I got a self hosted skill in Cloud Foundry, that uses Node js, Typescript and Express.

The code looks like this:

const app: express.Application = express()

// Skill entry point
const skill = application.getSkillBuilder.createSkillForWebService()

const adapter = new ExpressAdapter(skill, config.global.verifySignature, config.global.verifyTimestamp)

const PORT = app.listen(process.env.PORT || config.global.port)

app.post("/", adapter.getRequestHandlers())

const listener = app.listen(PORT, function () {
     const { address, port } = listener.address() as AddressInfo
     logger.debug("%s listening to %s%s", app.name, address, port)
})

So when I deploy into a lower environment and a new instance of the Express adapter is created, I pass false for verify signature and verify timestamp.

And it works when I test it on an Alexa device and on the Alexa developers console.

And when I deploy it into production and a new instance of the Express adapter is created, I pass true for the verify signature and verify timestamp.

And I get this error: AskSdk.Request verification failed Error, Missing Certificate for the skill request

Am I missing something in my code??

Do I need to upload the certificate in the Developers console??

Thanks in advance for your help

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