Decrypting HTTPS Traffic from Android Apps via Fiddler?
I ran into the same issue.
First - make sure you have it all set up correctly on Fiddler on your PC:


Goto Tools-->Fiddler Options-->HTTPS and make sure the first 3 check boxes are   checked.
Click "Export Root Certificate to Desktop" and copy the cert file from your desktop to your device/SD card
In your device, goto setting-> security -> Credential Storage-> Install from SD Card , and install your certificate.


That's it.
worked for me :)