I think this is something that you will need to consider - acknowledge or not acknowledge when a down line member logs in after a period of inactivity.
Personally, I do follow up with affiliates to see what kind of assistance is required as it is good to understand what is needed in order for the program to be a success.
Definitely do a follow up. Just do a quick check in and then wait for a response. If your assistance is required, you will hear back.