Difficulty re-attaching the oil fill tube to new coolant tank

[Stroked & Blown]

I replaced my coolant tank and have gotten all of the coolant lines re-connected on the back side of the firewall.

BUT I am having a very difficult time getting the oil fill tube re-connected to the manifold on the engine-bay side of the tank. I literally spent an hour trying to wiggle it onto the manifold port including using some WD-40 to help it slip on, but I just can't get it to seat more than a few MM. The spring clamp is being held wide open w/ spring clamp pliers and I've triple checked to make sure it's not interfering.

I searched a bit and found others with similar problems, but does anyone have any tips/advice on how to get the tube to fully seat?

I was thinking about warming up the tube a bit (hot water maybe?) to see if that helps, but open to other ideas.

TIA