I am backing up continuously to a separate external hard drive. I am using BitDefender Total Security. One problem that I am presently experiencing is with MS Windows Store. It no longer works. I cannot load or use any Windows apps. I have no idea what I did to cause this though it occurred a short time after downloading and installing BitDefender. After some internet search I found that I could open the Windows Store via WSReset. exe but none of the apps work. It is not a major problem. My Windows 8.1 now runs similarly to Windows 7. I can still find most of the applications or programs I want but not via Windows Store. It is mostly just annoying.
Steps you can try to resolve this...
Try shutting down "exiting" out of bitdefender to see if the issue remains, if it does not, then Bitdefender is blocking something.
You have already tried the windows store/apps resetting of the cache. Which allows the windows store to open but not the apps. So next i would run a "sfc /scannow" to see if there is anything corrupted.
If the sfc scan finds problems, but are not able to fix them then you can run a "dism /online/cleanup-image/restorehealth" command to try and resolve the issue.
Both of these commands need to be run in the Command Prompt
try 1st: "sfc /scannow"
Only use if 1st fails at fixing what it finds: "dism /online/cleanup-image/restorehealth"
need to be run as Administrator and without the quotation marks.