If you are logged in at RepublicBank.com -
To enable the account select "My Settings" from the top of the screen, then scroll to the bottom and select "Rename & Hide accounts" from here you'll see your account with an eyeball icon to the left. If there's a line through it, it means it is hidden if you click on the icon it will remove the line and turn blue which will unhide your account.
If you are logged into the app -
To re-enable the account from the mobile app, you will need to click the Gear icon in the top right corner for Settings and then select "Account Preferences" You should see your account there and to un-hide it, select "Edit" in the top right, then tap the eyeball icon so that there is no line through it and select "Done" in the top right. You may then need to log out and log back in for the account to appear as normal.