The recipe shows up in JEI, but the brewing stand cannot proceed after creating an akward potion and trying to add soul sprout.
Existing Ice Resistance Potions can also not be extended with Redstone Dust.

I was able to confirm and fix the issue in 1.21. This will be resolved in 2.4-b04c

What version of Cold Sweat and Minecraft is this? It worked correctly in my testing using the latest beta on 1.20

1.21.1, with Cold Sweat 2.4-b04a