PRIVATE_ORG_MODE_DOMAIN_WHITELIST not accepting domain

Hi,

Sorry for my english.

I have a deployment for several years now with IS_PRIVATE_ORG_MODE set to True and two different domains in PRIVATE_ORG_MODE_DOMAIN_WHITELIST configured flawlessly, but adding a third domain just won't let registering accounts with this third domain. I've tried several domains and it always get a 400 response on registering although both original domains work perfectly.

Any clue why is this happening?

Thanks in advance