The Release file in repository is invalid, or public key is outdated

Hi,
I tried installing version 2.3.10 and encountered the following problem while installing new module/language/extension at setup tab.
“The Release file in repository is invalid, or public key is outdated”
I checked System Diagnostic page and shows everything is working fine. I further drill down issue and found one related topic, here is url: but there is no solution written there.

Please help me; I even tried to install previous version of 2.3.9 but still no success.