www.makemkv.com

I installed MakeMKV 1.14.4 for Windows yesterday, and purchased it online, and got over email a purchase registration code of the form "M-[42chars]_[23chars]"

When I launch it, it says "This application is too old. Please download the latest version or enter a registration key [OK/Register]". The OK button terminates the app. I clicked the "register" button and typed in my code (I tried both the full version, and a version without the leading "M-" in case that was mistake).

In both cases it just pops up a dialog box that says "Registartion [sic] code is incorrect [OK]", and simply terminates the app when I click OK. (I also tried using the beta code that had been posted to this forum, but the beta code gives the same results as my purchased code).

I tried emailing support@makemkv.com yesterday but maybe they're too busy to respond, so I thought maybe this forum might get me going quicker. If anyone knows how to register MakeMKV, I'd love to know!

Try copy/paste to apply the code (NO leading/trailing spaces). Typing it in by hand is just too prone to typos.

Same with my Key. Copy/Paste also don´t work.

Copy from what email program?

Some email programs (Outlook to name a particularly common one) will insert formatting information in to a copy-to-clipboard. When you paste it in somewhere else (like MakeMKV in your case), that formatting information causes issues. It's a tech support nightmare. Basically, if you copy from any Microsoft product, you have invisible garbage in with what you think you have.

I keep a text editor (no special formatting codes allowed) open all the time, so I paste anything copied from a "fancy" program into a blank buffer, then select and re-copy the text to the clipboard, without the invisible formatting information.

In Windows you can use the buildin "Editor" app (same as Notepad) for this. Use the search function to find it.

I tried everyting, also by the new Version. Nothing worked. I saved the Key years ago in the editor app and gad never Problems. But after a new Windows 10 Installation I can't unlock it with my key.
I hope my english is not that bad. (I'm German)