Question about SANDISK ExtremePRO

Why does this reader only recognise UHS-II cards, but not UHS-I? On two different devices with Windows 11, this reader recognises a UHS-II SDXC card, but not UHS-I SDXC cards (I tested three different such cards). I am really getting desperate. Do any of you have an idea what the problem could be? Thank you and LG, Marcel