SSL certificate problem

Hello, I get this error when I try to download updates:

SSL certificate problem, verify that the CA cert is OK. Details: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

I cannot understand if it’s a problem of mine or of the provider’s. I have read many posts about this, but the proposed solutions are quite different one from another and I am not sure what needs to be done.

Thank you for your help and happy new year!
Laura