I don't have any experience of Outlook or trouble shooting it.
It's possible that the 2004 update is the cause, but have a look at the suggestions in this article, but disregard what looks like a paid for program of the OST to PST Converter.
https://www.msoutlookhelp.com/blog/outlook-ost-cannot-be-opened-resolve-error/These cmds may or not help in resolving the problem which you can try if those steps are unsuccessful.
Open a Command Prompt (Admin) and enter -
dism /online /cleanup-image /restorehealth
sfc /scannow
Enter exit to close the cmd window and let me know what they report.