How to restore missing Shared Groups in Passwords app on iPhone after reinstall?

Good day to all of you!

My partner and I have been using the Passwords Shared Group functionality on our work iPhones for many months now. This last week, to install specific upgrades my partner's company wiped their iPhone and did a fresh installation. Now when we go into the Passwords app the Shared Groups section is missing and none of our shared passwords are available on their iPhone.

To try to fix the issue we removed them from the shared group and tried to add them in again. Trying to join the group they get a message that they were removed from the group or the group was deleted. Creating a new group and inviting them to the new group causes the same message to appear.

I saw a post somewhere that said creating the shared group on their phone and sharing it to me might clear up the issue. This is not possible though since the Shared Groups section is completely missing from their Passwords app.

What do we need to do to get our Shared Password group working on their phone again? Both of our phones are running iOS 18.3.1. We have deleted the Passwords app on their iPhone, restarted the phone, reinstalled the Passwords app, and then restarted the iPhone. The Shared Groups section is still missing from the app.

Thanks in advance to any helpful advice you can provide.

Have a great day everyone!

Shadallark_Cloudy

[Re-Titled by Moderator]