There are a few things that I noticed that might discourage the turtles from using the new dock... first, is the tile slippery? If so, they'll need some form of traction to climb onto it. Second, there really isn't much of an incline, I notice that when my turtle goes up to bask he uses the submerged part to gain a grip so he can hoist himself up, maybe your turtles are having difficulty because there isn't a lot of dock in the water. Lastly, how stable is it? If it doesn't allow the turtles to get totally dry thats problematic for a few reasons, one of which is that it will lead to shell rot if they can't dry their shells completely. Shell rot will also occur if they don't bask because they aren't comfortable on their new dock, so its a good thing you've noticed and are addressing it.
Perhaps you could try adding some traction and maybe a ramp, I forget exactly what other people on here have used but you can search the forum... i think they may have used some rubber mats... there are a variety of things you could use, just make sure the adhesive you use isn't toxic.
If alterations don't work, maybe just buying the large sized zoomed dock will make your turtles happy
