Synology hyper backup log in issue

Hi there,

My brother and I both have 2 bay Synology NAS drives, and have attempted to use Hyper Backup to secure our family photos remotely over the Internet.

After realising Safari's pop-up blocker was blocking the pop-up window that allows log in to my brothers NAS (that's what we assumed!!) I managed to finally log-in and start the back up to his M3 iMac.

BUT, my brother who did the same, can not get the pop-up window to appear for Hyper back up log-in (as shown in the attached). I have a Intel i& iMac.

Can anyone please help with what could be preventing this window from popping-up please. No add blocker or the software installed on my brother M3.

Thank you for any, and all replies.

David