There are various errors and reasons for receiving them. What specific error you are getting?
Certificate errors typically occur when there is a problem with a certificate or the server's use of the certificate. There are various types and causes of certificate security alerts, warnings and error messages and they can vary depending on what browser you are using. Common causes can be as simple as the system time (clock date/time) not being correctly set as noted by Demonslay335 or failing to update root certificates.
Why do certificate errors occur?
How do I know there is a certificate error?
Can I go to a website that has a certificate warning?
Can I turn off certificate checking?
I'm getting errors on websites I always visit. What should I do?
Is it ever safe to ignore a certificate warning and continue to a website?
What about expired certificates? Is it okay to go to a website with an expired certificate?
What do the different certificate errors mean?
The following table contains a list of common certificate errors and information about what they mean.
This websites security certificate has been revoked.
This websites address does not match the address in the security certificate.
This websites security certificate is out of date.
This websites security certificate is not from a trusted source.
Internet Explorer has found a problem with this websites security certificate.
This message is telling you that there may be both secure and non-secure content on the page. Secure and non-secure content, or mixed content, means that a webpage is trying to display elements using both secure (HTTPS/SSL) and non-secure (HTTP) web server connections...Internet Explorer blocks non-secure content by default and is set to prompt you when this is happening.
Only secure content is displayed notification in Internet Explorer 9 or later
There is a problem with this website's security certificate. The security certificate presented by this website was not issued by a trusted certificate authority...This problem can occur if the client computer's clock is set so that the date/time is later than the expiry date of the web server's SSL certificate.
Internet Explorer: There is a problem with this website's security certificate
The certificate error is generated when the Microsoft Outlook settings Signature has an image that was loaded using the Upload Image option in the Insert Image dialogue box.
Error: The identity of this web site or the integrity of this connection cannot be verified
Information you exchange...there is a problem with the site's security certificate.
The security certificate was issued by a company you have not chosen to trust.
The name of the security certificate is invalid or does not match the name of the site.
The security certifcate has expired or is not yet valid.
This page contains both secure and nonsecure items.
Common HTTPS Secure Server (SSL) Certificate Errors
There is a problem with the site's security certificate warning
Secure and NonSecure Items Warning Message