The function keys on the Sony VAIO Computer is controlled by "VAIO Event Service". The issue may occur if this program is not installed correctly, corrupted or if the Service is missing in the Computer.
It is required to re-install the VAIO Event Service in the Computer to resolve the issue.
You can download and install the VAIO Event Service from the below link.
Download the VAIO Event Service here.Please click on the "Download Now" button on the page to download the file.
You may save the file on the Desktop.
Then, double click the file to begin the installation.
After that, please restart the Computer for the settings to take the effect.
Re-installing the VAIO Event Service will fix the issue with the function keys.