The domains do not fit on your account as we lowered the domain limit on Johnny accounts to just 5 back on January 28. https://helionet.org/index/topic/66787-domain-limits/
You're allowed to keep your existing domains as-is (you have 8), but if you want to make any changes, you must comply with the new limit, which for you would require removal of at least 3 domains to bring the total down to 5. If you want these two added, you'd actually need to remove 5 domains (so you have 3 + the 2 new ones).
If you need more than 5 domains, you will need to upgrade your account to Tommy (which still has a 10 domain limit), or Morty (15 domain limit), or more (by having more than one Morty account).