What kind of computer are you trying to connect your phone to?
It sounds like a USB issue where your P8Lite isn't actually automatically mounting when you plug it in. If the operating system on that computer doesn't detect and mount any external USB device, no application installed on that computer is going to be able to detect and access that device. In this instance, as an example, if it's running Win10 and for some reason your phone isn't automatically mounting itself when you plug it in, you need to look in the Windows Device Manager, and check the USB section if there's anything there flagged as a problem. Since you already tried different USB cables, are you plugging your phone directly into a USB port on the computer, or into a USB hub or some other pass-through USB device?
Also when it involves USB cables, while they all look similar, they are most definitely not the same in quality and reliability. If you're buying your cables at bargain-level prices from off-brand sources, buy a good, branded USB cable instead. They don't cost that much more and they're constructed with higher quality wiring inside, better insulation and shielding on the outside, and more dependable plugs on each end. That results in a better, less problematic file transfers and power delivery. Most people just settle with mysterious issues that randomly occur with cheap USB cables so for a couple of bucks more per cable you can at least take the cable out as part of problem when trying to diagnose some connectivity problem.
But if you have determined your P8Lite is mounting itself properly, have you tried reinstalling the HiSuite utility on this computer? It could just be a matter where the driver/firmware needs to be reloaded for some reason.