The 340 days embargo is madness. It looks like the system has suspicions or something!
I tried using our Macs instead of our iPhones, air dropping the invite. I might try accepting with a VPN set on some other countries, who knows it might be country specific...
I noticed another thing:
My sister is the 2nd person who entered the family. The 3rd and 4th person are getting kicked out. I am far from reaching the storage limit (about 80gb off).
When I enter a 3rd person, it will show iCloud+ for a while (possibly 24 hours), I can see us 3 in the Family storage break down. Then the 3rd person will be shown the 200Gb I pay for but without the iCloud+ features and that person will disappear from the Family storage breakdown. It is now only a matter of time before she gets the iCloud storage full message.
It seems the 3rd person's "instance" in the database is supposed to be synched but somehow it becomes orphaned and gets out of synch eventually.
I can't believe this issue is not widespread enough to draw enough attention at Apple.
I got used to iCloud so much over the years, it would annoy me to try and find another solution.