Trying to install all exported windows WEP Enterprise 802.1X Wireless certificates (.p12 extension) to a Samsung Android 4.0.3 tablet. With no certificate installer, Android certificate was installed from Google Play on the Tablet. The certificate file was opened, however, the error “No Certificates to Install” was displayed.
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).
Using a file manager tool, it seems that you could double click the .p12 file and it would open in the default browser and prompt you for the certificate key password. If this doesn't occur, it could be that you changed the default browser on the system and that new browser doesn't know how to read and prompt the cert password?