I just updated to the new AMD drivers(21.4.1), and PhoenixMiner seems to be choking(similar to when 21.3.1 came out with 5.5c. Radeon 6800 non-XT. Moving back to 21.3.2 for now.
It's not supported.
Added support for AMD Windows drivers 21.3.2, and 21.3.1 are.
Just add -clKernel 0 any drivers will be fine.