Welcome @kuxiang, to the community!
you are probably talking about the STM32H735G-DK, right?
If only the plastic caps (blue and black) have fallen off, the buttons are still operable and probably functional (reset and user button).
If, on the other hand, the entire buttons have been torn off, you would no longer have any of the above-mentioned functions, but you would not significantly disturb the other functions of the board. Nevertheless, in this case you should consider the possibility of repairing or re-soldering the buttons, depending of course on the extent of the damage.
Alternatively, you should inform your delivery service of the damage and request compensation.
Does it answer your question?
Regards
/Peter
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