DeepL API failure on Trados Studio 2021 SR2

I am using Trados Studio 2021 SR2 - 16.2.9.9198 and tring to use DeepL. I've got a DeepL Pro license(paid one) and pasted the API key as instructed but got ''Authorization failed, Please supply a valid API Key". I've added api.deepl.com on the white list with my anti-virus software - nothing done for the Windows11 security & network setting.  Anyone experienced the same issue and sorted out? Grateful for advice.

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