Well, if you have used email assets as the stream content of your original program then you'd have to clone the email assets and add them to the engagement program’s stream. Engagement programs don't resend emails to people who were already sent that email asset previously (from that engagement program, other program, campaign flow, etc).
Engagement program and/or stream could be different or the same for resend (at the very least, a separate stream is recommended as it could help keep things organized a bit).
However, nested default programs as stream content could get trickier! When using a nested program, the decision to send an email to a person is based on the program membership and program ID.
- If the record isn't a member of a program, it will be sent any emails that are part of the program once
- If the record is a member of the program, it won’t be sent the email
- If the record is no longer a member but received the email earlier through that program, it won’t be sent the email
When you use a program in a stream, it doesn’t matter if the record was sent that specific email before. As long as the email was not sent out before in that specific program, it can be sent again.
In any case, if you want to resend something, it’s safest to create a new program and smart campaign. As stated above if you have email assets in the stream, then you would have to create them again in case you want to resend them.