Please help… GT-i9505

Medusa cannot connect with GT-i9505 !
All JTAG wires are connected correctly and I get this error

Code:

Please connect the target device and power it on...
Checking data...
VREF = 0.12V is less than required level. Please check target device power supply.
Medusa JTAG Firmware version 1.1.0.
Medusa JTAG Hardware S256 revision D.
Detected TAP ID: 4BA00477, IR Length = 4.
Detected TAP ID: 2071B0E1, IR Length = 11.
Medusa JTAG Firmware version 1.1.0.
Medusa JTAG Hardware S256 revision D.
JTAG speed  : 1000 KHz.
VREF level  : 1.79 V
CPU        : Qualcomm APQ8064T
Core ID    : 2071B0E1
ERROR[004]: Medusa Device Server did not replied to HELLO command.
Checking data...
Medusa JTAG Firmware version 1.1.0.
Medusa JTAG Hardware S256 revision D.
Detected TAP ID: 4BA00477, IR Length = 4.
Detected TAP ID: 2071B0E1, IR Length = 11.
Medusa JTAG Firmware version 1.1.0.
Medusa JTAG Hardware S256 revision D.
ERROR[000]: Unable to halt core.