Zoho Projects users get added to .eu domain, but site is on .com domain

Zoho Projects users get added to .eu domain, but site is on .com domain

Hi,
2 questions:
1. I paid for an extra user in Zoho Projects and asked him to register on our domain. He is forwarded automatically to the .eu domain and the site is on the .com domain. I tried the steps described in other forum posts, nothing worked... How do I solve this? (We're based in Belgium, EU)

2. What's the correct way to add more users in the future?