Error querying Personal Access Token

I am using this query from your Postman examples to retrieve the PAT schema:

{
	"schema": {
		"criteria": {
			"searchQuery": {
				"key": {
					"$TREE": "/PersonalAccessToken"
				}
			}
		},
		"scope": {
			"fields": {
                "key": 1,
                "type": 1,
                "name": 1,
                "queryable": [1],
                "attributes": 1
            }
		}
	},
	"compatibility": {
		"SchemaObject": "1.0"
	}
}

I get this error:

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    <div class="error-page">
        <div class="error-page-content">
            <h1>Page not found</h1>

            <div style="padding-top: 35px">
                Oops! We weren't able to find your Azure Front Door Service
                configuration. If it's a new configuration that you recently created,
                it might not be ready yet. You should check again in a few minutes. If
                the problem persists, please contact Azure support.
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I excecuted this query directly in Postman; every Environment I previously set up (that was successful) generates this error. I also tried it with ../Read and ../SchemaRead, with the same error.

Why would this message appear instead of the regular-formatted error: data { Msg: [ {...} ] } ?

If the query itself is wrong, what is the correct one?

This query uses the Bearer Token Authorization and is set up correctly.