Alan D. Snow

What happens if you download the grids first and disable PROJ Network?

That was perfect, thank you. If you have a moment to try out your original set up with PROJ NETWORK and pyproj 2.5, that would be helpful.

If you set the environment variable PROJ_NETWORK to ON, it should enable it: https://proj.org/en/stable/usage/network.html#how-to-enable-network-capabilities

See: https://pyproj4.github.io/pyproj/stable/transformation_grids.html

I am guessing that the issue is in PROJ and #1133 uncovered the issue. However, I could be mistaken. I haven't had time to dig into the issue or raise...