If your web hosting provider is using outdated software on their server, you may see an error like this when trying to update your theme or plugin.
An error occurred while updating [theme or plugin name]: Download failed. SSL: certificate subject name ‘*.sucuri.net’ does not match target host name ‘churchthemes.com’
Or, it might read like this.
An error occurred while updating Resurrect: Download failed. SSL: no alternative certificate subject name matches target host name ‘churchthemes.com’
This is because your web hosting provider’s server is using an old (and possibly insecure) version of CURL and/or OpenSSL that does not support SNI (Server Name Identification).
Please ask them to update their software to the current version or move you to a server that is up to date. If they will not do this, we recommend switching to a new hosting provider (see our recommendations). Very few web hosting providers are running software old enough to cause this issue.
You can update manually (see instructions for themes and for plugins) while you wait for your web host to update their software.
An article from Yoast provides more background and technical details on this.