If the manual method does not work then you can go for any third-party tool to export OLM file to Windows Outlook. Here I would like to highly recommend you to use the best vMail OLM to PST Converter tool which is a one-stop solution to migrate Mac OLM file to PST format. The tool imports the OLM file to Office 365 and a Live Exchange Server directly. It supports 30+ MBOX platforms like Apple Mail, Thunderbird, Spicebird Mail, etc.
Know more info- https://www.vsoftware.org/olm-to-pst-converter.html
Know more info- https://www.vsoftware.org/olm-to-pst-converter.html