under back of phone hold off button until it vibrates three times,in flashtool start the flashing procedure but with phone not connected until the diagram pops up then connect it and see if that works
Seems working, maybe just dont got the good firmware? Still bootloop
16/030/2015 07:30:26 - INFO - Flashtool Version 0.9.19.10 built on 04-10-2015 21:00:00
16/030/2015 07:30:26 - INFO - Executing search strategies to find proxy selector
16/030/2015 07:30:26 - INFO - No proxy found for IE. Trying next one
16/030/2015 07:30:26 - INFO - Strategy firefox failed trying next one : No Firefox installation found
16/030/2015 07:30:26 - INFO - No proxy found for java. Trying next one
16/030/2015 07:30:26 - INFO - Syncing devices from github
16/030/2015 07:30:27 - INFO - Scanning devices folder for changes.
16/030/2015 07:30:31 - INFO - Pulling changes from github.
16/030/2015 07:30:32 - INFO - Devices sync finished.
16/030/2015 07:30:32 - INFO - Device disconnected
16/031/2015 07:31:06 - INFO - Flash canceled
16/031/2015 07:31:33 - INFO - Selected Bundle for Sony Xperia SP (C5306). FW release : 12.1.A.0.266. Customization : USGeneric
16/031/2015 07:31:34 - INFO - Preparing files for flashing
16/032/2015 07:32:55 - INFO - Please connect your device into flashmode.
16/033/2015 07:33:08 - INFO - Device connected in flash mode
16/033/2015 07:33:09 - INFO - Opening device for R/W
16/033/2015 07:33:09 - INFO - Reading device information
16/033/2015 07:33:09 - INFO - Phone ready for flashmode operations.
16/033/2015 07:33:09 - INFO - Opening TA partition 2
16/033/2015 07:33:09 - INFO - Current device : C5303 - YT910Q04TQ - 1272-3352_R1B - 1272-3352_12.1.A.1.207 - GLOBAL-LTE_12.1.A.1.207
16/033/2015 07:33:09 - INFO - Closing TA partition
16/033/2015 07:33:09 - INFO - Start Flashing
16/033/2015 07:33:09 - INFO - Processing loader.sin
16/033/2015 07:33:09 - INFO - Checking header
16/033/2015 07:33:09 - INFO - Flashing data
16/033/2015 07:33:10 - INFO - Loader : S1_Root_7054 - Version : R5G006 / Boot version : R11B023 / Bootloader status : NOT_ROOTABLE
16/033/2015 07:33:10 - INFO - Max packet size set to 64K
16/033/2015 07:33:10 - INFO - Making a TA backup
16/033/2015 07:33:10 - INFO - Opening TA partition 1
16/033/2015 07:33:10 - INFO - Start Dumping TA partition 1
16/033/2015 07:33:16 - INFO - Finished Dumping TA partition 1
16/033/2015 07:33:16 - INFO - TA partition 1 saved to C:\Users\***\2015-10-16_07-33-10\1.ta
16/033/2015 07:33:16 - INFO - Closing TA partition
16/033/2015 07:33:17 - INFO - Opening TA partition 2
16/033/2015 07:33:17 - INFO - Start Dumping TA partition 2
16/033/2015 07:33:18 - INFO - Finished Dumping TA partition 2
16/033/2015 07:33:18 - INFO - TA partition 2 saved to C:\Users\***\2015-10-16_07-33-10\2.ta
16/033/2015 07:33:18 - INFO - Closing TA partition
16/033/2015 07:33:19 - INFO - No flash script found. Using 0.9.18 flash engine
16/033/2015 07:33:19 - INFO - Opening TA partition 2
16/033/2015 07:33:19 - INFO - Writing TA unit 00002774. Value : [01]
16/033/2015 07:33:19 - INFO - Closing TA partition
16/033/2015 07:33:20 - INFO - Processing partition-image.sin
16/033/2015 07:33:20 - INFO - Checking header
16/033/2015 07:33:20 - INFO - Flashing data
16/033/2015 07:33:23 - INFO - Opening TA partition 2
16/033/2015 07:33:23 - INFO - Closing TA partition
16/033/2015 07:33:23 - INFO - Opening TA partition 2
16/033/2015 07:33:23 - INFO - Processing amss_fsg.sin
16/033/2015 07:33:23 - INFO - Checking header
16/033/2015 07:33:23 - INFO - Flashing data
16/033/2015 07:33:25 - INFO - Processing amss_fs_1.sin
16/033/2015 07:33:25 - INFO - Checking header
16/033/2015 07:33:25 - INFO - Flashing data
16/033/2015 07:33:27 - INFO - Processing amss_fs_2.sin
16/033/2015 07:33:27 - INFO - Checking header
16/033/2015 07:33:27 - INFO - Flashing data
16/033/2015 07:33:28 - INFO - Processing apps_log.sin
16/033/2015 07:33:28 - INFO - Checking header
16/033/2015 07:33:28 - INFO - Flashing data
16/033/2015 07:33:30 - INFO - Processing cache.sin
16/033/2015 07:33:30 - INFO - Checking header
16/033/2015 07:33:30 - INFO - Flashing data
16/033/2015 07:33:34 - INFO - Processing fotakernel.sin
16/033/2015 07:33:34 - INFO - Checking header
16/033/2015 07:33:34 - INFO - Flashing data
16/033/2015 07:33:37 - INFO - Processing kernel.sin
16/033/2015 07:33:37 - INFO - Checking header
16/033/2015 07:33:37 - INFO - Flashing data
16/033/2015 07:33:41 - INFO - Closing TA partition
16/033/2015 07:33:42 - INFO - Opening TA partition 2
16/033/2015 07:33:42 - INFO - Processing system.sin
16/033/2015 07:33:42 - INFO - Checking header
16/033/2015 07:33:43 - ERROR - Processing of system.sin finished with errors.
16/033/2015 07:33:43 - INFO - Ending flash session
16/033/2015 07:33:43 - ERROR -
16/033/2015 07:33:43 - ERROR - Error flashing. Aborted
16/033/2015 07:33:43 - INFO - Flashing finished.
16/033/2015 07:33:43 - INFO - Please unplug and start your phone
16/033/2015 07:33:43 - INFO - For flashtool, Unknown Sources and Debugging must be checked in phone settings
16/033/2015 07:33:44 - INFO - Device connected in flash mode
16/033/2015 07:33:45 - INFO - Device disconnected
16/033/2015 07:33:47 - INFO - Device connected in flash mode
16/034/2015 07:34:04 - INFO - Device disconnected