OpenSSL self-signed certificates, Windows 10 laptops, and "This certificate has an invalid digital signature" error

I have the following:

1. OpenSSL-generated, Self-signed Internal CA cert
2. OpenSSL-generated Internal-CA signed, wildcard cert

This cert protects our internal websites. e.g. "myservice.corp.example.com"

In this example, the wildcard cert has the following fields of note:

CN = ".corp.example.com" DNS = ".abc.corp.example.com" DNS = "*.xyz.corp.example.com"

(i.e. those last two are SANs)

To make the CA chain acceptable to the OS, I install the CA certs on workstations.

This works fine on macOS. "Fine" == "Green site-is-secure icon in browsers". I install the CA cert in the site-wide keychain, and set the Trust to "Always Trust"

However, on Windows 10, I install the CA cert via the Certificates snap-in (or by right-clicking on the cert -> Install). No matter what I do, I get the following error notices in the cert:

1. Certificate -> General -> "The integrity of this certificate cannot be guaranteed. The certificate may be corrupted or may have been altered."
2. Certificate -> Certification Path -> Certificate Status -> "This certificate has an invalid digital signature"

Finally, the RSA key is 2048 bits, and the signature algorithm on both the CA cert and the self-signed cert are sha256

I've scoured the web but can't find any resolution that helps me yet, but it appears it may be one of the following:

1. Issuer and Subject can't match. Or must match? not sure. (They do match in my CA cert)
2. Minimum key length not satisfied. (we are using 2048 bits, though)
3. something else?

My problem is I don't even know how to troubleshoot this on Windows. I'm a Linux admin. So, requesting troubleshooting steps and possible resolutions.