Outlook not exporting pst files

Hi everyone,

I normally backup my e-mail on a .pst file, but the last time I tried to do it, the option for exporting and importing .pst files is not available for me. I've got an office 365 Home Premium licence, using it in Windows 8.1. 

So, I really don't know what to do for having it available again. 

I tried uninstalling and reinstalling my suite, cleaning the register... pretty much everything I can, and I need to make that backup again. 

Any suggestions?

Regards,

MSB