The certificate is a so-called Cross-Signed-Certificate, i.e. there are 2 certification paths available. Current software and browsers should automatically access the new certificate chain already stored in the store. Older software unfortunately still access the old invalid path, which is why the CA file on the server must be exchanged.
The new certificate chain is already delivered with new orders or renewals. This is unfortunately not possible for existing certificates. If you need the new certificate chain, you can download it from the following link: