iPad Pro 12.9” 2021 HDR effect gone

After updated to iPadOS 14.6 I found my iPad Pro 12.9” 2021’s display doesn’t have any HDR effect anymore wether on Apple TV+, Netflix, YouTube, or the HDR video shot from my iPhone 12 Pro without changing any settings. It’s really obvious compare to my iPhone 12 Pro playing HDR content side by side. The bright part is not glowing anymore. It used to be exactly the same effect as my iPhone. Is it a bug on iPadOS 14.6 or do I miss any proper set up? Does anyone has the same issue here?