Software per Internet Point, Hotspot WI-FI, Phone Center

[redarrow]

Gateway 192.168.1.1

Manager 192.168.1.45

Phones: 192.168.1.51 & 192.168.1.52

Only 192.168.1.52 is working the other gets a ring tone but does not send the call through.

[mdeioris]

It's absolutely sure that there is some difference in phones configuration. There aren't other possible causes for your problem.
Try to factory reset both phones, remove them from the workstation monitor and configure them again. The phones should automatically appear in workstation monitor. Remember that the only difference in the phone configuration must be their IP.