The return process in case of a warranty case always goes via your Dealer/Webshop.
It could be that another process is in place. If that is the case, it is mentioned on this page
To analyze a problem, please check the troubleshoot pages and see if the issue is hardware or software related or can be fixed by our advise
If you do not know what kind of problem it is, please contact the Tacx support here
Tacx gives 2 years warranty on its Trainer portfolio.