: On Windows, ensure you are running the application as an administrator, though some users report this may interfere with drag-and-drop features. Try Insecure SSL : In some cases, navigating to Menu > Impactor > Insecure SSL

Understanding why this error happens is the first step toward fixing it: How To Install Apps With Cydia Impactor - No Jailbreak

But Apple had changed the rules. Again.

: Cydia Impactor now largely requires a paid Apple Developer account to function properly.

Since late 2019, Apple made server-side changes to its authentication process that fundamentally broke Cydia Impactor for most users.