Opener is not sent to people who have been connected for more than 48 hours

For example, if you selected it like this, an opener will only be sent once you have been connected to the contact for more than 3 days.

This is because LinkedIn no longer displays hours once the connection has lasted more than a day, only days. Since 48 hours is 2 days, 49 hours must appear as 3 days in the list.