Hi @Majestic_Songbird4731,
Thanks for writing in, and I'm sorry you're stuck with this right when you need your invoices. I can imagine how annoying it is to keep hitting that error every time.
First things first, please don't worry about the admin part. Removing your colleague won't change anything here. Admins do get the invoice email notifications, but actually viewing and downloading the invoices is tied to the contract owner alone, not to how many admins are on the account. So that wasn't the reason behind the error, and you're free to add her back whenever you like. You'll find the full details on how this works here: https://adobe.ly/4dSkshW
As the contract owner, your invoices sit under Admin Console > Account > Billing History, and from there you can download them as PDFs or email them across to yourself and others. One quick thing to keep in mind: after a payment goes through, it can take up to 24 hours for that invoice to show up, so if it's a very recent one you're after, that timing could be part of it.
Since you're already in the right place and still seeing the failure, could you try it once on a different browser, or in an incognito/private window with any ad or script blockers turned off? These little things sometimes come in the way of the download without any obvious reason.
Do give that a try and let me know how it goes. If it's still not working, just tell me which browser you're on, whether the error shows up on both View and Download or only one of them, and the month(s) you're trying to pull, and I'll dig into it from my end.
Thanks,
^AV