@Zili Yang Thanks for using Microsoft Q&A Platform.
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Please make sure you are using correct subscription key
or API endpoint.
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I have reproduced this everything works well on my end. Here's the CURL command again for your reference please try this:
curl -H "Ocp-Apim-Subscription-Key: <yourkeygoeshere>" https://api.bing.microsoft.com/v7.0/search?q=microsoft+devices
Replace YOUR_SECRET_KEY
with your actual subscription key. If the issue still persists, I would recommend regenerating your subscription key in the Azure portal and try again.
I hope this helps.