How can I access /sdcard/ when I connect to PC (MTP) I'm running a Nexus 5 (Android 6.0.1) 

Today I have created a WhatsApp backup file and wanted to copy it to a new device. I can confirm the file existence in ES File Explorer.


(Click image to enlarge)  

However, I cannot find the file when I connect my Nexus 5 with a USB (MTP).


After further checking I found the file is stored in /sdcard/WhatsApp, while my PC is connecting to /Internal Storage/WhatsApp

(Click image to enlarge)  

But I cannot find /sdcard/ in my PC...

To make things more complicated, when I reboot the N5, the file appears again /Internal Storage/WhatsApp/

I've been a long time Android user since Motorola Milestone. I'm not a dev but luckily I have the experience in tackling such issue. But for a normal user without in-depth computer knowledge, this inconsistent behavior is just weird. There's a long way for Android to catch up with iOS in terms of user friendliness.
/sdcard and /Internal storage are same directory.  

As for why the file does not appear instantly is because of a bug in MTP mode as MTP cache is outdated until a phone reboot. If you do not wish to reboot the phone, 

Possible Workaround:


Settings &rarr; Application Manager &rarr; All Apps tab &rarr; Media Storage &rarr; Clear Data  
Install SD Scanner app &rarr; Open App &rarr;  Click on Start Rescan


Tested and Works on Android 5.0 Lollipop