my P8 (Android Lollipop) can't be recognized by my PC (Windows10) I'm the owner of a Huawei P8. At the beginning the phone was recognized by my PC as a second hard disk but lately I touched something (I don't remember what).

Now, when connected to the PC, the phone is set to charge but it is not seen as a mass storage and neither the computer nor the phone seem to recognize each other. I went through almost all the settings but couldn't find ANYTHING on how to make the computer react to the phone.

USB debugging cannot be used. I would like NOT to have to root the phone or do strange installations – and online the only kind of answer I found was that I have to do a hard reset of the phone. Is it true? Can anybody give me a less traumatic suggestion?
I believe I had the same problem on my Huawei P8. My Windows 10 PC would not recognise the phone, although it would charge it. 

The problem was not with the cable or PC - the same cable and PC would work later on, with the only changes made, made to the phone.

I didn't have the same qualms about rooting or 'strange installations', so I rooted using KingRoot then used "SG USB Mass Storage Enabler" on the Play store to toggle the storage mode. 

This worked for me, even though SG Mass Storage Enabler is made for Samsung and Sony devices, and hasn't been updated since 14 Nov 2013.

A disadvantage of this method was being unable to uninstall KingRoot. This may be my own fault though, possibly due to me corrupting the KingRoot install by trying to replace it with SuperSU.

This method was the only method I tried that worked. Things that didn't work included trying to backup without root to factory reset (this is data and application dependent on whether you can backup without root), trying to activate USB debugging, ADB, Hisuite and HDB.

If a custom recovery is already present on the phone, then SuperSU could be used to root instead of KingRoot, which is adware at the least, and also seems to prevent itself being removed from outside the app.