Issues connecting with cockpit to Ubuntu

[HeLiOn]

So I have this NAS running on Ubuntu 20.04 (if I got the version correctly).
I installed cockpit on it. The installation went without a hitch, yet whenever I try to log in through the web interface using the credentials, I get the following error:

 

Upon inspecting that particular log, I found the following line:
 

cockpit-tls[3372]: cockpit-tls: gnutls_handshake failed: A TLS fatal alert has been received.

It occurs once, and only when I try to log in.

Also here's a picture with the actual screen:

 

I have no idea what could be causing this, guys. Can anyone help?
I already posted this issue on their github page, but no one there seems to answer.

[Master Disaster]

Its a certificate error. From what I'm reading on GitHub it seems as though Cockpit has to be accessed through HTTPS on the browser, using HTTP won't work. I'm not sure how you can get a certificate for your loopback subdomain though? All the people who fixed this issue did so by using Apache/NGINX, obtaining a certificate using Cerbot then setting up a HTTPS reverse proxy.

 

One person says that adding "AllowUnencrypted = true" to "/etc/cockpit/cockpit.conf" and restarting the cockpit service allows it to work internally through HTTP but you lose external access entirely.

[HeLiOn]

13 minutes ago, Master Disaster said:

One person says that adding "AllowUnencrypted = true" to "/etc/cockpit/cockpit.conf" and restarting the cockpit service allows it to work internally through HTTP but you lose external access entirely.

Thank you for replying.

And... I already did that. I was getting a certificate warning on the browser.
Placing that line in the config, got rid of the warning, and I've been able to reach the login page without any issues.

Now, I took your advice and tried connecting using http, instead of https. Something else happens now:
I'm not getting that error that directs me to the log. Instead I remain on the login page. The browser even offered to remember the credentials.
And when I check the log, I get a different error:
 

cockpit-tls[2159]: cockpit-tls: gnutls_handshake failed: The TLS connection was non-properly terminated.

 

[HeLiOn]

Update:
I tried connecting using Edge, and it worked. I successfully accessed the cockpit control panel.
The 2159 error is only caused when I try logging in using Opera... which kinda sucks, cause it's my browser of choice.

 

I'll mark this one solved, for now. Thank you for your assistance, @Master Disaster!