No internet connection (i.e. no updates, no plugins)

Hello all,

I have a WP installation that won’t talk to the internet.

Here’s what I have done so far:

1) installed a Ubuntu 16.04.03 LTS server with the LAMP package and phpmyadmin on virtual machine
2) sudo apt-get update && sudo apt dist-upgrade
3) configured MySQL
4) sudo apt-get install wordpress
5) configured apache so that https://myserver.mydomain.local/wp points to the WP homepage
6) completed the WP configuration wizard

Up to here: no problems. WP loads, I can login, I can configure settings. Great.

But here’s the problem: the server is behind a proxy and can’t connect directly to the internet. So I added these lines to /usr/share/wordpress/wp-config.php
/* Configure proxy Server */
define(‘WP_PROXY_HOST’, ‘1.2.3.4’);
define(‘WP_PROXY_PORT’, ‘3128’);
define(‘WP_PROXY_USERNAME’, ”);
define(‘WP_PROXY_PASSWORD’, ”);
define(‘WP_PROXY_BYPASS_HOSTS’, ‘localhost’);
define(‘WP_USEPROXY’, ‘TRUE’);

Restarted the server and nothing. Still doesn’t connect. I tried to do an update to WP 4.9.2 but the server doesn’t find it automatically. Instead it says 4.4.2 is the latest version (which I think is a bug, I would think that I get a warning if the check fails). Trying to install plugins directs to a page where I’m asked to enter an ftp-server address.

This is what my Squid says when WP tries to connect to the internet:
IP_OF_MY_WP_SERVER – – [26/Jan/2018:15:44:08 +0100] “POST https://api.www.ads-software.com/plugins/update-check/1.1/ HTTP/0.0” 501 3861 NONE
IP_OF_MY_WP_SERVER – – [26/Jan/2018:15:44:08 +0100] “POST https://api.www.ads-software.com/themes/update-check/1.1/ HTTP/0.0” 501 3857 NONE
IP_OF_MY_WP_SERVER – – [26/Jan/2018:15:44:08 +0100] “POST https://api.www.ads-software.com/core/version-check/1.7/? HTTP/0.0” 501 4157 NONE

Googling for the 501 error told me to install php5-curl, which isn’t necessary because it’s been superseded by another package which is already installed.

Another thing I did was to add
export http_proxy=https://IP_OF_PROXY:3128
export https_proxy=https://IP_OF_PROXY:3128
export ftp_proxy=https://IP_OF_PROXY:3128
export HTTP_PROXY=$http_proxy
export HTTPS_PROXY=$https_proxy
export FTP_PROXY=$ftp_proxy
to /etc/profile to allow the OS to talk to the internet, which works great. apt-get works, wget works.

Does anyone have an idea what to do? I’m at my wits end.

Regards
JBerner