I'll start by mentioning that the certificate does work on most devices.
The certificate has multiple chains. The problematic one (I think) goes something like this:
COMODO RSA Domain Validation Secure Server CA COMODO RSA Certification Authority - **EXPIRED** AddTrust External CA Root - **Expired**
How do I fix the certificate chain on IIS/Windows server so old android devices (Android 5 and under) can still connect via HTTPS?
What should I have in the certificates manager? And how can it be done without a whole server restart?