Our server is behind a proxy. Checking for updates works fine, but plugins cannot be updated automatically. Workaround: download with browser and install as ZIP.

Error when plugin update is clicked (questionnaire is just an example):

{{Debugging output enabled
cURL request for "https://moodle.org/plugins/download.php/11327/mod_questionnaire_moodle31_2016020201.zip" failed, HTTP response code: HTTP/1.1 403 Forbidden

line 1354 of /lib/filelib.php: call to debugging()
line 440 of /lib/classes/update/code_manager.php: call to download_file_content()
line 409 of /lib/classes/update/code_manager.php: call to core\update\code_manager->download_file_content()
line 120 of /lib/classes/update/code_manager.php: call to core\update\code_manager->download_plugin_zip_file()
line 1084 of /lib/classes/plugin_manager.php: call to core\update\code_manager->get_remote_plugin_zip()
line 1265 of /lib/classes/plugin_manager.php: call to core_plugin_manager->get_remote_plugin_zip()
line 2276 of /lib/upgradelib.php: call to core_plugin_manager->install_plugins()
line 199 of /admin/plugins.php: call to upgrade_install_plugins()

Error fetching plugin ZIP.

line 392 of /lib/classes/update/code_manager.php: call to debugging()
line 412 of /lib/classes/update/code_manager.php: call to core\update\code_manager->debug()
line 120 of /lib/classes/update/code_manager.php: call to core\update\code_manager->download_plugin_zip_file()
line 1084 of /lib/classes/plugin_manager.php: call to core\update\code_manager->get_remote_plugin_zip()
line 1265 of /lib/classes/plugin_manager.php: call to core_plugin_manager->get_remote_plugin_zip()
line 2276 of /lib/upgradelib.php: call to core_plugin_manager->install_plugins()
line 199 of /admin/plugins.php: call to upgrade_install_plugins()

Downloading mod_questionnaire ...
<- https://moodle.org/plugins/download.php/11327/mod_questionnaire_moodle31_2016020201.zip
-> ... Error}}