My S4 has suddenly stopped to connect to any computer. I tried with 3 different cables and 2 PC's with win7. I can't see it as a hard-drive. I can't see it in the device manager either (should I)? Any help would be welcome. Many thanks!
Uninstall the drivers from Samsung and download and install then again on your PC this seems to be an driver problem. If this not resolve your problem come back and I can suggest other options.
Does your phone recharge when plugged in?
Any sound on your PC when you connect or any notification on your phone about being connected via USB?