I don't know why It only shows up as 14.9Gb and what the yellow region is, but i have noticed similar with other USB sticks.
Hi,
IIRC the "Yellow" area is reserved it's where it creates it's own in internal file/allocation structure.
It's possible you unfortunately have a dodgy/broken stick.?
((There are some dodgy sticks out there that are manufacture defects, but have been relabled))
One last test, use gparted again, remove the partition table.
This time create a new partition starting at 2 but with a size of only 1024
See if that works, if not, looks like it maybe broken.
If it works repeat, but start at 2 and make it 4096
If it works repeat, but start at 2 and make it 8192
Dave