As Tom’s explained, existing investors have pre-emption rights - which you’d expect too, if you had invested last time. If it’s any conciliation, it looks like I won’t have a chance to invest either! Although there will be several rounds of invites.
In retrospect there probably are other ways that Monzo could have set up this round of crowdfunding, to ensure that more users had a chance to invest. We’ve suggested a few ideas earlier in this post, I’d be interested to hear your thoughts.