To re-enable a disabled list member please follow the below steps:
1. Log into your List Owner board.
2. In the List Member Management panel, enter the disabled email address in the "Search members" search box.
3. Click the mini-menu (3 dots) at the right end of the row and click the "Enable delivery" function.
If the list member was disabled due to bounces, then please make sure you resolve the issue that is causing the bounces before enabling the disabled list member. Otherwise, they may become disabled again.