How to register purchased Mikro if it's aready registered to another account?

Contact N.I. Account Support with proof of purchase and picture of serial on bottom of device and they will see if they are able to help. , In case that you need guidance contacting support : How to contact NI Support and How to get in touch with our Customer Care (simply choose did not help when chat-bot did not help). if having problems getting things to work then please read the suggested help pages.

In case that the webpage doesn't work then since functionality or lack of same could be a browser issue then also try another browser with no extensions and all cookies accepted (my suggestions for alternative browsers would be e.g. Firefox, Chrome, Vivaldi browser and Opera browser , depending on what you do not usually use)