When you downgrade from Pandora Premium to Plus or ad-supported Pandora, you will not be able to access your on-demand music collection or custom playlists. However, your collection and playback history will be stored in our servers for when you return to Premium. The same will go for your family members that were on your plan previously.
In the meantime, I do see that you were able to resubscribe successfully. You would need to re-invite those family members in order for them to receive Premium again. From my end, it looks like there are 2 invited family members that don't have Pandora accounts and 1 that has an account but hasn't accepted the invite yet.
If you've already sent an invite to a family member and they haven't received it, make sure that:
You've sent the invite to an email address your family member can access (not necessarily the email address on their Pandora account);
They check their spam folder, as the invite may have ended up there.
Once they've received your invite email, they'll simply select Accept Invite, and either log into their existing Pandora account or create a new account.
If you continue to have trouble with this, please let me know and I can create an email support case for you.