Hello Matt B
I understand that you have been unable to open Personal Vault on your MacBook Air. Since it still works on your iPhone, the vault and its files are accessible; the issue is more likely related to the browser verification session on the Mac.
Please note that Personal Vault is not available directly in the OneDrive app on macOS. You need to open it through the latest version of a supported web browser, as shown in the screenshot below.

Reference: Protect your OneDrive files in Personal Vault
Please try the options below and check whether the issue continues:
- Install or update Microsoft Edge, Chrome, or Firefox, then open OneDrive on the web in a private/incognito window.
- Temporarily turn off any ad blocker, privacy extension, or VPN, as it may prevent the separate verification page from loading.
- When prompted, choose a different verification method, such as Microsoft Authenticator, SMS, or email code. As a workaround, you can also review the sign-in approval methods linked to your Microsoft account. Make sure you have another working verification method first, then remove only an unused or affected method and try opening Personal Vault again.
Please let me know how it goes after trying these steps, and I'll be glad to continue looking into it with you.
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