emacs listing packages error in process sentinel

Question

I'm new to emacs, have installed emacs26, and I use a proxy server. When I tried to add packages it is showing this error:

error in process sentinel:

Error retrieving: https://elpa.gnu.org/packages/archive-contents (error connection-failed "failed with code 110" :host "elpa.gnu.org" :service 443)

I added the following code:

(setq url-proxy-services
   '(("no_proxy" . "^\\(localhost\\|172.16.2.30\\)")
     ("http" . "localhost:8080")
     ("https" . "localhost:8080")))

But I still get the same error.

Answer 1

It appears that

(custom-set-variables
 '(gnutls-algorithm-priority "normal:-vers-tls1.3"))

fixes the problem.

Cf. https://emacs.stackexchange.com/a/56067/795