Dear Aazura
Welcome to Microsoft Community.
We have learned that you successfully subscribed to other calendars from the web in outlook.com and you successfully subscribed and can see the calendars in outlook.com, but you cannot see the associated subscribed calendars in mac calendars.
May I ask how you are viewing the calendar of your outlook account in the mac calendar?
If you have added your outlook account to your mac calendar, then it is recommended that you remove the account and re-add your outlook.com account.
Alternatively, you can download the outlook app directly on your mac and configure your outlook account to check if you can see your subscribed calendars in the calendar.
If none of the above works, we recommend that you resubscribe to the calendar outlook.com. Then reconfigure your account in Mac Calendar or Outlook.
I hope the above information can help you.
Best Regards,
Peter.Y-MSFT | Microsoft Community Support Specialist