No problems here with accessing the toppr.com website,

• https://www.toppr.com/

What happens if you try to access the website?

See also:

• https://support.mozilla.org/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

Can you attach a screenshot?

• https://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

• Use a compressed image type like PNG or JPG to save the screenshot
• Make sure that you do not exceed the maximum size of 1 MB

It looks fine to me. Some more information would help cor-el.

Have you used that site successfully before? Are you having trouble with any other sites? Do you have another browser that you could try? Do you have access to another computer that you could try? Your System Details show no plug-ins or extensions. Is that correct?

Some response would help.