Same on iOS, incredibly frustrating. Have you found a solution?
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Of course I tried that with this /c, so I can't see this post now! LOL
I'm writing this in my browser.
Have you tried this setting

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I do not have any of those switches on that setting page turned on.
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Iβd check βshow hidden in communitiesβ
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None of the switches on that settings page are set, including "Show Hidden In Communities"

Long press the hide viewed posts button and a menu will appear.
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Long pressing "Hide Read Posts" and no menu appears for me on Android.
The wording is slightly different, if you're referring to something else.
It's a little unwieldy but if you view your profile and go to the hidden posts section, you should be able to edit or reset the list there.
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