Do you mean MPEG-2 encoder or the MainConcept encoder?
What error message and number are you getting - please quote the full message?
Check that your Antivirus/Firewall is not blocking the program from accessing the Internet and the Folder Protection /Ransomeware feature is not blocking the program or parts of the program and/or quarantining them if it is you need to fix this by adding exceptions for the program and unquaratine any modules that have been blocked - how you do this depends on your AV.
Several different AV programs have been know to cause issues with false positives and some Magix programs.- these include Windows Defender, Avast/AVG, BitDefender and Kaspersky,