Hi anonymous user
I have looked into the backend logs and I can see that the requested authorization key is not authorized.
This could happen if you have copy pasted the key and special character are added to it (starting or ending of the string). You can either use command prompt and paste the key to see if there are any special character/space added to the key or you can covert in it UTF-8 format to verify it there is any special character and remove it from the string.
I will suggest you copy the keys again using "copy to clipboard" option from Event Grid Topic under the key section
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