The following does not apply to you. Please just follow the steps for the v1.9.x to v2.0.x migration.
You will have to delete the files
Signer_v2 from the ConfigurationPath,
%programdata%\win-acme by default. Then you will have to manually renew once to
create a new account with the ACME server.
The reason for this is that v2.0.11 runs on .NET Framework 4.6.1 which required us to drop support for the elliptic curve account signers.