Unable to export .p12 from Keychain access

I'm facing weird situation. For Apple Push Notification I can't export .p12 file from Keychain access. I can highlight both items and click on Export 2 items but after that nothing happens. All steps are correct as I've been doing it all the time. It seems something is wrong with keychain access or my Mac? I did it successfully few days back for another key and it worked, exporting for this old one doesn't work now. I don't think there is any error or problem in generating certificate otherwise it should work for older keys.

Solution

Rebooting machine worked in my case.