I can't install any add-ons on latest stable release

Hello to everyone. I’ve just installed ford the third time coreelec with kodi 19.5 matrix version on a S905X Amlogic box. It’s the Z11 pro model with 2gb ram and 100mbps ethernet. Right now it’s booting from micro-sd card and it’s a clean install. The big problem is that I can’t install any of the add-ons from the official repository. I see that I can’t upload any file because I’m a new user so no log file I can provide. I have tried some fixes from another threads but no one could help in my case. I don’t understand why this happens because my internet connection works ok, i don’t have a proxy configured and the only add-on that I could install was the gismeteo from repo after fresh install. Can someone explain why this problem occurs because it’s something that I’ve never seen. In parallel I’m using a HP t620 thin client with libreelec matrix version and I never experienced this. I also mention that I don’t want to use anything pirated and dodgy on my boxes, just the legit content from the default repos. Sorry for my bad english. I will try to make me understood as much I can.

Maybe you don’t have DNS servers set?

You’re right, I never set these before. I will try today when I’m home.