Bluetooth file transfer between Mac and android phone I am trying to transfer a couple of images from android device to mac. As per the following links it seems that this transfer should be possible:

Apple support
HowToGeek - how-to-use-bluetooth-file-transfer-between-os-x-and-android-5.0-devices

But the android device is not visible in mac's list of discovered devices and similarly mac is not visible in android's discovered devices list. I have tried searching for possible gotchas but unable to find any. 

Android device specification:
OS : 5.0.2 (Lollipop)
Bluetooth version: 4.0 

Mac Specification : MacBook Pro (Retina, 15-inch, Mid 2015)
OS : El Captain
Bluetooth version: 4.1 (LMP version 0x7)  

I can do the transfer by other means but trying to understand that what's the trouble here. Any help will be appreciated.
If you have done everything in that HowToGeek article correctly, I don't see how it's not working. So maybe go through it step by step and check that you didn't miss anything.

Next thing may sound stupid, but have you tried turning both devices/Bluetooth on those devices off and on again? A good old reboot may be enough to fix this problem.

If both of my above solutions don't work, then I cannot help you further, however, I can give you an alternative (although that isn't what you really wanted). I use a messenger called Telegram and send images (sometimes files) from my Phone to my Laptop and vice-versa. Good thing is that there is a client for almost any platform which means you can access your messages (and in this case images) on any device you want.