Here is how my problem started (the phone not being seen problem may have existed prior to this). I connected my phone to my computer (a sound played during connection). Autostart opened Windows Explorer showing the phone storage. I double clicked to find the folder where my videos were. I right clicked the video I wanted to transfer to my PC, chose 'cut', right clicked the desktop and chose 'paste'. The video disappeared from the folder on the phone, but was not on the desktop. I refreshed the desktop, but the file still did not appear.
I restarted both the PC and the phone. Tried reconnecting and started getting notifications in the taskbar 'installing drivers', as if the phone's driver's had been uninstalled. The driver installation failed. I tried a Windows update and found updates available, but the installation failed (code 800F020B). I ran System File Checker and repeated the above, but the update failed. Strangely though, if I opened Explorer, the phone showed up (however on some occasions it didn't).
I therefore installed 'Undelete 360'. Tried to access the phone to retrieve files, but the program couldn't see the phone (even though I could access files via explorer). I thought it may be the software, so I tried 'Remo Recover', but the same happened again.
I have also tried uninstalling drivers (unknown device in Device Manager) and restarting, but to no avail.
I have the latest version of HTC Sync Manager installed, but this program seems to be of no use.
The phone is in USB debugging mode and when attached to the PC is showing 'MTP Enabled' (I can't find anyway to change this). Android version 4.3. The only other noticeable problem on the phone is that HTC Sync, which was supposed to be in sync with Gmail, is hsowing 'Sync Off' and I can't switch it back on.
I would appreciate any assistance in resolving this. My objective is to retrieve the video files I tried to 'cut' and 'paste'.