Membership Reminders Not Being Sent Out and Not Working

Hello,

Membership reminder emails are no longer being sent out. See the following messages from the system:


6 hours
[SYSTEM] - Email Invoice for Order - #3199 was sent to Mark Edwards (Axiom Realty Group Inc)
6 hours
System wrote a note on Mark Edwards (Axiom Realty Group Inc)
Memberships Real Estate Licensee Membership expired due to failed payment for Order #3199
6 hours
System wrote a note on Mark Edwards (Axiom Realty Group Inc)
Unable to renew membership due to credit card decline. This client is no longer a member.
6 hours
Mark Edwards (Axiom Realty Group Inc) has a New Order - #3199
$ 55.00

How can we ensure to have the system send out a reminder email prior to the expiration of a membership?

Thank you for any help you can provide.