Which versions? Has anything changed? Does this have anything to do with it?

Advisory: Mailchimp announces changes to free plan - Announcements - Sage CRM - Sage City Community

I believe we are using Sage CRM 2020 R2.2 1219. I do not know that anything specific has changed. I can say that when I look at the mail chimp logs from the time that it became an issue and there is a lot of "Error when kicking off MailChimp tasks" with a lot of code that I do not understand. 

I wouldn't have anything to do with the changes in the free plan, we are and have been on a paid plan for years. Also, the segments do actually push over to mail chimp and within mail chimp, I can use them, I just cant use them when I am setting up the actual mail chimp campaign in CRM, where you link it to the segment, there are only segments from prior to the issue starting listed, and any segments I have sent over after that, while accessible in mail chimp, do not populate in the campaign in CRM. 

If they push over to Mailchimp and you're getting stuff back in the logs this side, I would raise a case with Mailchimp. If you're on a paid plan, then you should have support. Sounds to me like the issue is their side. Post the relevant part of the logs (minus any identifying information and potential password)

It's possible that this is a technical issue that requires some troubleshooting, but it's also possible that there could be a compatibility issue between CRM and Mailchimp. Have you tried reaching out to the support team for either software to see if they can offer any guidance or assistance? On a side note, if you're looking for crm and project management software that integrates well with CRM, you might want to check out some of the options that include project management features. There are a lot of great solutions out there that can help streamline your workflow and keep your team organized.