Specific Shockburst rounds gem (unable to use)

I have a Shockburst Rounds gem lvl 19, 20% and 4 sockets that wont allow me to use it. I have crafted another gem of the same type and it allows me to use it. Also when click the arrow to expand the details, it expands as if I am selecting my other gem (explosive shot). Shockburst rounds has no dmg amount on the main Skills page. Any thought?