Thanks for posting and welcome to the Community! Sorry to read that you are having issues with your QC20 controls after an update.
Can you please let us know if this issue persists only with the Samsung A51 or on all devices you are using your headset with? I would also like you to use the headset with a few other streaming services on the device to see if you can control anything.
We look forward to hearing back from you with the result of these steps.
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