This can happen if you are entering the email address in to an email field in RE that is not mapped to a field in LO. There are multiple email fields in RE, but only one of them can be mapped to LO. To see which field is mapped in LO, follow the steps below.
  1. Data Management > select Luminate Configuration
  2. Click Map Custom Fields
  3. Compare the email field in LO with the mapped email field in RE (this is the field you should add the email to)