Bug with certificate generator

I tried to generate a certificate, the process completed without errors.
But the browser did not accept this certificate. I disabled ssl and enabled it again and selected Lets Encrypt certificate.

Afterwards I updated apt-get update and apt-get upgrade , restarted all services. Could not start nginx service. I restored the server from a backup, but for some reason my panel version became 1.5.1, although previously it was 1.8.10

How can I safely update the panel to the current version?