Cannot install "node-red" snap

As you noticed I am new in this forum. But reason why O am writing is a preoblem what I having during installation.

I have installed Ububtu 18 LTS. Ihave onstalled snap and after "snap install node-red" command I having fallowing error message:
(error: cannot install "node-red": Post x509: certificate signed by unknown authority)

What I have done wrong to have this message?

This error was caused by FW rule. That's mean if you https policy has been set to inspect everything, then error occur.

To solve it you just need to add exception for and that's it. All will run perfectly.

To be sure just first after making changes on FW check:
sudo dpkg-reconfigure -p critical ca-certificates
and then
snap install node-red