You'll get lots of recommendations - PB Blaster, heat, sledgehammer, etc. I hope one of them works for you.
Just in case they don't - I tried pretty much everything (for several seasons), and never got mine free.
I bought 2 18-inch hitch extensions (e.g.
https://www.amazon.com/CURT-45796-Receiver-Tube-Extender/dp/B0007M1FNM - you can get cheaper brands, but I trust Curt or Reese).
We add those two extensions on the ramp, along with a deep-drop stinger. You're not supposed to tow with 2 extensions, but 5 MPH on the ramp is pretty safe.
I add the deep-drop stinger for 2 reasons:
1) I don't want to dunk my nice Weigh-Safe ball-mount in salt water
2) On the ramp, your boat is always bow-high (even on a shallow ramp, and more so on a steep one). So the stern floats first (or last when retrieving). The limiting factor is the bow - so dropping the bow a few inches with the stinger levels the boat just a little and floats the bow more easily. You don't have to back quite so far into the water. Hope that was clear as mud...
That combination works for us - with our GMC 2500HD, we can launch and retrieve on most ramps with the tires in the water, just before the wheels would touch.