SD Card not detected?

Hey Guys,

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I just got my new Steam Deck OLED a few hours ago. I'm now trying to install EmuDeck and when choosing the Rom location in custom install-method I can't select my SD Card. The button is shown but it says there is no sd card detected so I can't choose it.
In Gaming mode the card is present as well as in desktop mode and the correct space is shown. Also I tried to reformat the card a few times already. Doesn't seem to help. Do I have to grant permissions somewhere or something like that? And if, where?