Issue with Steam after installation.

I bought a new PC (Beatcom) with AMDsoftware graphics software and installed Steam by running steam.exe for the first time. An error message appears telling me that the update is impossible because there is no internet connection, except that I have an internet connection. I tried my Wi‑Fi network and my network share, but nothing works… no DNS problem. I also checked every time all the network settings and they are good. I also tried deleting the installation files except the .exe… Disabled by fire… disabled the Steam client in Task Manager… but nothing works, the error message appears every time….