The last version you registered is v0.1.0, as you can see in https://github.com/JuliaRegistries/General/blob/master/P/PDBTools/Versions.toml. You are supposed to register v0.2.0 first, then v0.2.1, then v0.2.2.
For practical purposes, you can just release v0.2.0 now, with the changes for v0.2.1 and v0.2.0 included.