As THCsoftcore suggests open it up and take a look the fault may be obvious i.e battery leak
Ideally it would be something relatively straight forward like a flat battery (no leaks) so it would just be a case of fitting an infinikey (if you can get hold of one)
Me! Being on a tiny island in the middle of nowhere means learning to do all my own repairs Thailand is a bit more central but still unlikely that you will find anyone local either.
Luckily the CPS2 B board has been fully reverse engineered so even the gnarliest repair is only a matter of time and energy.
That being the case; lets do some remote arcade board repair coaching! Post some pictures of what is wrong and the advice will roll in