Posted 06 January 2016 - 07:06 AM
I am no expert but it looks to me like you have joined a number of us who have found many of our Apps, including the Store itself, trashed --- following the November update. The trigger for this seems to have been using the PowerShell command to re-register apps. The command 'Get-AppxPackage --- etc' is the smoking gun. It has been quoted many times on various forums.
Various fixes have been tried repeatedly without success, so we are waiting for Microsoft to come up with a solution in the hope they have been working on it. However, nothing encouraging has emerged so far.