Citi Double Cash CLI impossible?

I first was approved for a Citi Double Cash 3 years ago (680ish) with a starting limit of $600. Which was shockingly low compared to my other cards ($2k-$10k). I have made several attempts to increase my credit limit but have been declined everytime. Even with my score reaching 740, I was still denied. Last week marked 3 years with my Citi double cash card and they just denied my CLI again.

Am I missing something?