To view HTTPS traffic in Fiddler on Lollipop and newer, you need to add the FiddlerRoot certificate (DO_NOT_TRUST_FiddlerRoot) to the system list of CAs otherwise it simply won't work.
You need to have the CertMaker for iOS and Android installed because the default SSL certificate does not work properly on iOS/Android. It can be downloaded from the Fiddler Add-ons page:
http://www.telerik.com/fiddler/add-ons
After generating a (new?) root certificate open the .cer in the stock browser or Chrome (Firefox uses its own certificate system thus doesn't install to Android itself) and install the certificate for "VPN and apps" and name it Fiddler or whatever you want.
The certificate will be located in /data/misc/user/0/cacerts-added/.
Remount /system R/W as root if you haven't already (mount -o remount,rw /system).
Move the .0 file to /system/etc/security/cacerts/ and chmod the file to 644.
Reboot, and you should see HTTPS traffic from Android.