These are public forums, not a contact for any Magix staff, and confidential data, like your serial number, should never be posted here. To do so is to risk your software being hijacked. Hence, I have edited your post to remove it.
Please tell us exactly which version and edition of Movie Edit Pro you currently have, and which version you are trying to update to. Also, is your update Service still current, i.e. have you paid the currently annual fee to allow you to continue to update your software or, alternatively, do you have a subscription for the software? Without one of these you will not be able to update your software.
Please help us to help you by supplying a lot more details about the problem!