Hi Cary,
Have you uninstalled any browser like Chrome or Firefox before the issue occurred?
What’s your default browser now?
First, please try to reassign a default browser in Windows. Go to Start > Settings > Control Panel > Programs > Default Programs. Choose a default program as you want and then check the result.
If the issue still exists and you are using Internet Explorer as your default browser, we can try resetting Internet Explorer settings.
To do this, please start Internet Explorer. Go to Tools > Internet Options > Advanced > Reset.

For more information and other possible methods, please refer to the article below and see if the issue can be resolved:
Hyperlinks are not working in Outlook
Any updates, please post back at ease.
Regards,
Perry Pan
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