MDaemon Let's Encrypt certificates not working on Apple products

Something has broken relating to this root certificate expiry

https://scotthelme.co.uk/lets-encrypt-old-root-expiration/

I have had to update the Acme client on my Exchange Server systems to generate a new Let's Encrypt certificate which works fine, but there is no obvious way to do this with MDaemon.

Could you guys please investigate?

I have 2 servers demonstrating this issue. The certificates themselves expire in December 2021.

There are no issue on Windows Clients only Apple clients. Apple FireFox also works fine