Thank you for the details.
According to your screenshots, you use .NET Framework version 4.0. Please install SQLBackupAndFTP for .NET Framework version 4.0 and check if it resolves the issue. You can download this version at https://sqlbackupandftp.com/download page by clicking the "SQLBackupAndFTP for older .NET Framework v4.0.0" link.
SQLBackupAndFTP version: 11.4.1 requirements .NET Framework version 4.6.0 or above.