iThemes Security Pro 2 questions. Both are about scanning. Does not connect and cannot determine or find out whose certificate, how to solve?

Question

Information Security

Good afternoon. There are 2 questions regarding the IThemes Security Pro plugin.
There are 2 sites on which I get one error.
1. Unable to properly scan your site. TLS certificate issuer is unknown
Although the certificate is signed and valid until November 2020. and there are no problems with the Certificate.
2. Unable to properly scan your site. Unable to connect
Here it is generally unclear why it does not want to connect. how and where to look for the reason?
...
Stupid question, but still I'll ask:
Could there be a reason that you installed SSL and earlier the plugin was installed without SSL?

Answer 1

TLS certificate issuer is unknown

English on white - The issuer of the certificate is unknown. You need to look at the certificate, see who the publisher is and add his certificate to the trusted store. But on another computer it will be the same ...