I encountered a similar problem when my OST file stopped syncing in Outlook. I refreshed and repaired my profile multiple times, but there was no account update for the emails. I needed an offline copy that I could read and access outside of Outlook. I used the
DataVare OST to MHTML Converter Expert, and it was really helpful. It allowed me to convert the entire OST mailbox into MHTML format so I could open it in a web browser. All of my emails, attachments, and formatting appeared just like Outlook.
If your OST file is not syncing and you need a readable copy of your emails, it is as easy as converting your email to MHTML. It worked well for me and saved me from losing important data.