Questions about creaking wood floor

I installed 1/2" engineered hardwood several months ago using a Powernail 2000, cleats every 6 inches. It didn't take long for the joints to start making noise, sometimes it's like walking on bubble wrap.

I have tried some of the remedies found online such as powder graphite but no such luck. I had solid hardwood in my previous house and had similar issues but was able to quiet the squeaks by putting in screws from underneath. That does not seem to work very well with this flooring.

Does something like this lessen over time with a couple seasonal changes or is it likely to always be this way?

In hindsight, I should have spent the extra time and money and glued it down, but too late now