Install company's wireless certificate to Samsung Android 4.0.3. tablet
I had an issue with something similar a few years back - and I believe this thread helped (see Lynx's post about halfway down).  (I know it's a bit old - but I remember it being very helpful).

I believe the certificate also needs to be very generically titled "certificate.p12" or something like that (if I recall correctly).

Make sure it's in the root of your SD card and that you're trying to install from Settings >> Security >> Install from SD card.

You can also try and use this tool (not sure how secure it is - but it might help).