Welcome to the Magix user to user forums, so not a contact for any Magix staff, sorry.
Also, this is a public forum so personal information, like your email address, should never be posted here. Hence I have edited your post to remove it.
From where, exactly, did you purchase the software? It seems you might have bought it from another user, who had previously used it and not deregistered it? If so, you must contact the seller and ask that he informs Magix he is no longer the registered owner of it.
However, if you bought it new from a third-party seller, you need to contact them and ask for their help in resolving this. Magix will have no record of your purchase and so cannot help you.
If you purchased the software, new, from Magix, are you sure you entered your email address correctly on the registration screen?
Hello there, I bought the product from magix.com. I've been using it for a while. I got it with the e-mail address I use. I cannot use the product I have. Who can help? I have serial number and e-mail address.
Since you've owned the product for some time and clearly registered it previously why do you need now to reregister and activate it?
One thing you could try: go to your Magix account, log in, go to My products, find the listing for your software and deactivate the registration. Check the serial number (and check that your email address is correct on your account) and then try again to activate the product on your computer.
. . . . What trials and hoops to go through whil working. This reactivat demand is annoying . . . .
We need some context to this.
Assuming you have the same problem as the @kbaytan what changed on your computer, eg Windows upgrade to newer version, or have you re-installed the software on a new computer?
. . . . Use of Apple, (*.mov) may require the purchase of the new codex license . . . .
From your response this would suggest that you are not using Video Easy, ie you are using Movie Edit Pro, now called Movie Studio, or Video ProX.
Please create a new post in the appropriate section of the video forum, your issue has nothing to do with the OP's topic.
Also provide more information on:
Your computer system, see this topic fir what is required and please quote processor and graphics card(s) make/model in full.
A MediaInfo analysis of the video file you are trying to import. Download and install MediaInfo and see this tutorial on how to get the required data from the video file to post in your post.