I figured it out. BuddyPresss doesn’t use SMTP notification emails, so I installed FluentSMTP which is a free Plugin. Now all the notification emails are being sent and received by the members’ email accounts on the spot through my Gmail account which I set up in the FluentSMTP plugin.
The Group Directory page of Buddypress does not seem to a normal page, it’s more like an Archive template. I can see the issue does not persist on other static pages.
As we have no control over coding for third-party plugins nor themes, we highly recommend that you report this issue to the support team for this plugin so they may further troubleshoot and provide any recommendation (or possible fix) to resolve this issue.