I have just installed a clean version of LimeSurvey CE on a hosting server.

System configuration
LimeSurvey version: 3.15.5
LimeSurvey build: 181115
Operating system: Linux
PHP version: 7.0.32-1~dotdeb+8.1
Web server software: Apache/2.4.10 (Debian)
Database driver: mysql
Database driver version: mysqlnd 5.0.12-dev

I needed to make some updates to php settings to get the installation to run, but got through that hurdle. Now I am getting the behaviour described in the following Troubleshooting item (or very similar behaviour - I can do some minor admin tasks but not others. eg. Create a Survey page loads, but clicking Save redirects to login page)

www.limesurvey.org/manual/Troubleshootin..._you_to_login_screen

Any action in admin page will return you to login screen
This may happen for the following main reasons :

PHP sessions problems
UTF8 encoding problems
IE (6,7 and problems

PHP Sessions :

Update upload_tmp_dir and session.save_path in php.ini
Create the configured session and upload directories
IIS: Assigned permission to create and modify to IIS guest user account
Apache: Make sure your webserver has permissions to write into the configured directory
Check if the variable "session.use_cookies" in php.ini is set to 1.
Check the variable "session.auto_start" in php.ini. If it is set to 1, change it to 0.

UTF8 Encoding :

If you edit any file (most probably config.php) do not save it as UTF8 to support special language chars! Always save .php files as true ANSI/ISO format. Starting with 1.87 you can set the most important settings inside the application using the 'Global settings' dialog (like site name, administrator name, etc.).

IE Cookies :

IE (6,7 and does not support underscore "_" in the server hostname. If it is the case, the cookies are not managed and cookie(s) is(are) not set. So change the server hostname under apache or IIS.

I have updated the php settings as suggested, I have ensured that config.php is not in UTF8 format, and even though I am not using IE I have checked that the server hostname does not contain underscore.

I have googled and searched this forum and can't seem to find anything further than what is outlined in the troubleshooting documentation.

Does anyone have any ideas or advice on what I can try next?

Thanks

Through discussion with the hosting company, it was found that Varnish Cache was running on the server and clashing with the session. Disabling Varnish solved this issue.

Hope this information is helpful to someone in the future.

If i remind you can use Varnish cache for session : github.com/LimeSurvey/LimeSurvey/commit/...1c2a4d1beb1da7146ab4