when you say auto mode, does it mean you have configured "power inline auto" under gi1/0/46 ? 

Please check link below. You may need to configure "power inline auto" on gi1/0/46http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/release/12-2_44_se/configuration/note/ol14988.html

if the same phone works in another port, most likely that port is faulty. you might want to connect a machine on gig1/0/46 and see if it can connect to the network

What type of phone is connected on the port? Is this issue visible for all ip phones?