Q: iTunes 12 device icon greyed out?

If you have not already, restart the Mac and also Restart the iPhone (and iPod), then try it again.

Restart your iPhone, iPad, or iPod touch - Apple Support   (if it's an iPod touch)

Learn how to reset your iPod - Apple Support   (for other iPod models)

If they are both connected at the same time, connect them one at a time, to see if this problem is specific to one device only (and it's blocking the other device).  If you use WiFi for syncing, turn OFF one device so that the other can connect by itself, then reverse.

If you use WiFi to connect to iTunes, try using a USB docking cable instead, to see if that makes a difference.

If that does not help, please post back with additional details.

I have the same problem with the greyed out icon using  iPhone SE/iOS 10.0.2 with iTunes 12.5.1.21 on macOS sierra 10.12

Recently rebooted both but I'll try again. I need a fix fast.