Are you using Registry Cleaners of some sort? If so, stop as they are dangerous and if there's a restore button on it use that and see if the functions return. Have you any other A/V software installed? Is Windows up to date?
This can also happen if you are in the habit of using System Restore repeatedly. It should only be used in dire emergency.
Check for spyware using AdwCleaner and maybe MalwareBytes Free from this link: Anti-Spyware/Malware & Hijacker Tools
Run the Virtual Technician to see if it can find and fix problems.
If not lower down that page click Contact Support, tell Technical Support all that you've tried and ask for the case to be escalated.