When behind a firewall, I get "Cannot download package list. Error message: Unexpected response status code: 407" and GUI says "No packages to show". For OPM I use the same proxy settings as in browser and I have checked proxy IP address, port, username and password many times, so I don't get it why proxy does not let OPM authenticate. From browser I can access without problems both
http://packages.lazarus-ide.org and
https://packages.lazarus-ide.org and download packages by hand. Was there a known bug with proxy access fixed in some newer version? That seams to be my best chance right now.
That Lazarus was made with fpcupdeluxe (FPC and LAZ trunks on May 17th) that had OPM working and updating on original pc with internet access without proxy, and now copied to the same dir on target pc but behind proxy.
View / IDE Internals / About FPC:
Lazarus version: 1.9.0
Lazarus svn revision: 54956M
Lazarus build date: 2017/05/17
Lazarus was compiled for i386-win32
Lazarus was compiled with fpc 3.1.1