Hi @JustinMicheal-7973
Sorry I was not able to reproduce this issue in my lab.
According to your information, the archive mailbox could be displayed correctly in Outlook before, while after applying another retention policy to the mailbox, it disappears and can not be seen in both Outlook and OWA.
Have you tried cleaning the browser cache or use a different browser to access OWA?
If the issue persists, I suppose you may consider disabling and re-enabling online archive for this user to see if it can work for you.
If an archive mailbox is disabled, its contents would be kept for 30 days and if you re-enable it for the mailbox, the contents would be restored.
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