FOTA for CC3200 Flash file system Firmware upgrade

There really isn't much to go on based on what you provided. Generally there are 3 points of failure:

1) The upload process into the CC3200
2) The image file update process
3) A problem with the code in the image file

For #1:
-Do you have a checksum or some other method to ensure what you receive mirrors what is sent? If so does it match?

For #2:
-I'd make sure all return codes on the /sys/mcuimg.bin file operations are all good. That means return code checks on the sl_FsOpen, sl_FsWrite, and sl_FsClose both during the initial file update and then again when you're verification step is run (on the sl_FsRead instead of write).

-I can't check this right now but you might be able to use Uniflash to verify the image placed on the CC3200.  By clicking on the mcuimg.bin file clear out the "erase" & "update" boxes and leave "verify" checked.  The image name to verify should be placed in the URL field.  Without anything else being selected for other files when you click on program it may be able to verify the image.  Normally I like to check to see if this will work but my system is tied up and thought it might be worth a try.
 
For #3:
-The code may be running but hang, or fail, early in the process. What do you have in your code to verify it has started and when? Can you use Uniflash to flash the same binary on the CC3200 and have it run?

When you say reboot how is this done?