In the off case that you are unable to add a previously deleted contact, following these steps will help reconnect you with a once deleted user.
- Navigate to contacts
- Un-check the 'Show Online" check box
- Delete all variances of the user id
- EX: firstname.lastname@example.org may have multiple devices. Delete all contacts with the 'email@example.com'.
- Re-add the user
An alternative method to re-add a previously deleted user.
- Draft a message to the user you wish to read and follow the steps outlined here: https://help.binfer.com/hc/en-us/articles/115006668107-Sending-an-Open-Binfer-Message