Not only can't the RC be connected with a PC, I can't even connect the RC with my phone through the DJI go app.
Tried Android 4.2.6 and 4.2.4 version.
Tried at least two phones (both Android).

I'll try iPhone this weekend. But as the USB connection from RC won't be established to my laptop either, I think I open up a return case.

edit:
SOLVED by enabling USB debugging in the android developer options of the phone.

Hi there, had you sent the drone in already? If you haven't, maybe we can do the troubleshooting before sending it in. May I know the two mobile devices that you tried with? Please make sure that you had powered on the RC. And please also try to change another connecting cable, plug it into the bottom USB port, note to remove the left cable first. If it doesn't help, please provide me with a short operating video for a better confirmation. Thank you so much.

DJI Thor Posted at 2018-2-9 00:32
Hi there, had you sent the drone in already? If you haven't, maybe we can do the troubleshooting before sending it in. May I know the two mobile devices that you tried with? Please make sure that you had powered on the RC. And please also try to change another connecting cable, plug it into the bottom USB port, note to remove the left cable first. If it doesn't help, please provide me with a short operating video for a better confirmation. Thank you so much.

Hi @DJI Thor
thanks for the offer to help. I did everything like you told me to. Tried other cables, tried the bottom USB port, but nothing.
But here it comes. I got it solved and it's very easy. So please take this method to your manual/tech support/FAQ:

USB debugging must be enabled in the android developer options. It's nothing a normal user would consider, so I think it's worth to put that as a solution somewhere.

I think my two devices I tried with (OPPO R7 Plus and OPPO Find 7a) has other security settings for the installed app. So it seems they need the debugging turned on to grant access to some apps using USB OTG.