Please provide the launcher log. You can find them in %appdata%\CCBlueX\LiquidLauncher\data\logs and search for the most up-to-date log where the error occourd. Please upload it here or paste the content of the log to https://paste.ccbluex.net/ and share the paste URL.
In case we cannot help you immediately: Try to use the "Offline login" instead and then proceed to login into premium account inside the client. Also be aware that it requires you to use a Microsoft account.