I received a Workspace notification email, and I replied to that email via my email.
I did not get a response..

That is not how the Portal/Workspace communication works.
The Portal is designed with top-tier security in mind.
The Portal/Workspace notifications are sent from a blind 'noreply@..' email address.

Emailed replies to the notification emails (back to noreply@..) will not be received, as such an email is not in an end-to-end controlled environment, and therefore cannot be fully secured.

When you receive a notification email:
A. click the link within the notification email body to be brought to the Portal/Workspace login (or session resume), then on to the item in question to act on it.
B. manually enter the service provider's Portal (by website button, URL, or browser bookmark), then manually navigate to the item in question to act on it.

This is for the ensured security of your information, thanks for your co-operation.
see also https://help.dollaradaysites.net/knowledgebase.php?article=143