Rules not working on a shared inbox

This question relates to a work account, but my IT department don't support this kind of issue and Microsoft support can't help either, so asking here.

Some colleagues and I have set up a shared mailbox, with a rule to redirect all e-mails to said mailbox into our personal accounts. I set this up on the web browser version of Outlook, and initially it worked fine: e-mail arrives in shared mailbox, and also then arrives in our individual ones.

A new colleague was added to the mailbox, and he added a new rule for e-mails to be redirected to him. This turned off the redirect rule to the rest of us, so I deleted his rule, added him to the list of contacts on the redirect rule, but now nothing arrives in our personal inboxes.

The redirect rule is the only rule set up, but still doesn't work. I've tried deleting it and creating it again, changing it to forwarding, changing the people on the list etc. But all new e-mails just land in the shared mailbox and are never redirected to individuals.

Could anyone advise on what I could do to try and fix this?