[PretzelLogix]

Recently, I purchased a Lumia 640 and have used the "Tap to Share (NFC)" function with my friend (who also has a Lumia 640) to great success. Recently, I've tried to use it with friends who have Android phones (like Samsung Galaxy S5). Sadly, it didn't work.

Any ideas why this fails (and how to get it to work)?

[DJCBS]

It doesn't work. It recognizes the existence of an NFC device but WP doesn't communicate with Android.
Better use Bluetooth.

[PretzelLogix]

You say "Better use Bluetooth" -- How do I use BT to share pics with someone using an Android phone?

[psiu_glen]

You say "Better use Bluetooth" -- How do I use BT to share pics with someone using an Android phone?

Make sure Bluetooth is turned on for both devices, hit share on the WP...

Also, the NFC sharing doesn't work in either direction with WP from my Nokia 808 (running Symbian).