Hoi Denny,
Late response here, but when you say "cannot bootup" are you at least getting power or not?
If you are, then you might need to 'flash' the latest autoloader for the Key2, which is available at CrackBerry: [link|https://forums.crackberry.com/blackberry-key2-f472/key2-acq160-autoloader-may-2020-patch-1185582/|KEY2 ACQ160 Autoloader (May 2020 patch)|new_window=true], since BlackBerry no longer offers support to mobile devices anymore.
If you are not getting power, then you might either have a power issue or a faulty board.
Hopefully, this can be of assistance!