Put the summary of the bug you're having here

I had redstone beneath a piston, but once the redstone was active, the piston wouldnt fire

Steps to Reproduce:
1. Put a line a redstone
2. Put a line of pistons, facing up, directly above the redstone
3. This was done in an underwater area, but was completely dry, just in case this info is needed
4. Activate redstone. The redstone will now fire the pistons, and i have done a few tests.

From my tests, it appears that redstone signal directly from redstone (not torches or repeaters) will not go through blocks above them. I also did tests where i placed redstone, a block above the redstone, and a torch on the block. The torch does not change, whether the redstone is active or not. Unless redstone physics were changed (I dont know why that would be), this appears to be a bug.