Hi Velocity, and welcome to the forum!
There's a wealth of information here to help you on your credit journey.
If you've had the card for 6 months with no cli, then imo you are justified in asking for one. Just be sure and ask if it will be a soft inq or a hard inq when you're asking the CSR.
If it's a hard inq, I'd think twice, unless you really, really need the cli.