“Errors have been detected in the file C:\Users\AppData\Local\Microsoft\Outlook\outlook.ost” And because of this error users are unable to open Outlook app and access emails and other data.

To fix this error you can use SCANPST.exe (Inbox Repair Tool) available in Outlook installation folder to repair the OST file and after the successful repair, you can try to open the MS Outlook and check if the error is fixed or not.

(You can locate the OST file here: C:\Users\AppData\Local\Microsoft\Outlook\abc@xyz.com.ost)

If you are still facing the same error because OST file is highly damaged and Scanpst.exe is not capable to repair the OST file. In this case, you can try vMail OST File Recovery Tool to repair the OST file. This software can easily repair corrupted OST files and recover all emails, contacts, calendars, tasks, notes, journals, etc. Next, you need to export all recovered ost file data to PST file and import the PST file MS Outlook to accessing your emails without getting any error.

Learn More- https://www.vsoftware.org/blog/fix-error-have-been-detected-in-ost-file.html