The sender was already created, so the initCode should be empty. This error may occur if you attempt to create an account multiple times.

Solutions

1. If you are using an SDK like userop.js, permissionless.js, aa-sdk, or biconomy check that your account is being deployed is being deployed to the chain you expect it to. These SDKs should check against this error.
2. Remove the initCode from the user operation structure.