2019 Microsoft Office for Mac problem

You will need to contact Microsoft for assistance since this is a Microsoft product licensing/activation issue which only MS can resolve. When you use any of their current products, it either expects an activated copy of the licensed product, or it requires you to log into your MS 365 online account to have full functionality of their product.

If you are setting up a new Mac/OS then you will need to reactive any existing product since many times the MS license does not automatically transfer to the new system.

Note that Microsoft software updates and active product support for Office 2019 for Mac ended in Oct 2023. Provided you have a working version on macOS Ventura 13.7.2, you may only receive security updates through Oct 2025.

Since Microsoft ended active support over a year ago, the product may simply not be fully compatible with macOS Ventura 13.7.2. Take that into consideration when as HWTech suggests, you follow up with Microsoft on your current issue.

FYI, if your copy of Office is not activated, then you may not be able to save any file changes. I highly recommend you check with a quick simple edit since you don't want to find out after making a major edit. I've had this occur after making edits, but did not notice the warning prior to making changes.

You may want to check out LibreOffice as it doesn't have licensing & activation issues or even Apple's own Pages, Numbers apps.