I recevied support by email and what they told me worked. Here are the instructions:
Access www.wd2go.com and remove the device and to go to the drive dashboard and remove the email address and the set the remote web access again.
After this procedure I registered again my email address with a capital letter (because I read somewhere else that using the exact same email could cause issues) and I could finally access my files remotely.
I am glad WD support are actually reaching the customers to help the situation.
PS: I recommend using WD MyCloud app instead of the website, for speed purporses. For the application, you also have to remove the device and add it again manually.