Error: CGI program sent malformed or too big (>% bytes) HTTP headers: [X-Powered-By: PHP/7%ubuntu%

Let show us /opt/tinycp/logs/php_error_log

There should some error.

Here is the extract from php_error_log.

[06-Dec-2019 06:25:08 Europe/Warsaw] PHP Warning:  file_get_contents(https://tinycp.com/download/tinycp.stable.version): failed to open stream: Connection timed out in /opt/tinycp/www/inc/Core.class.php on line 156
[06-Dec-2019 06:26:33 Europe/Warsaw] PHP Warning:  file_get_contents(https://tinycp.com/download/tinycp.stable.version): failed to open stream: Connection timed out in /opt/tinycp/www/inc/Core.class.php on line 156
[06-Dec-2019 06:28:32 Europe/Warsaw] PHP Warning:  file_get_contents(https://tinycp.com/download/tinycp.stable.version): failed to open stream: Connection timed out in /opt/tinycp/www/inc/Core.class.php on line 156
[06-Dec-2019 19:21:36 Europe/Warsaw] PHP Warning:  file_get_contents(https://tinycp.com/download/tinycp.stable.version): failed to open stream: Connection timed out in /opt/tinycp/www/inc/Core.class.php on line 156

@ A 7189, I was having the same issue for a while and after some beers here is how I fixed it.

Before successful login, TinyCP is configured to check for updates and it compares it to your current version of TinyCP. The developer has since made the link for older TinyCP obsolete, TinyCP crashes and will not let you login. Crazy huh?

To fix this you need to disable the function in /opt/tinycp/www/login.ophp by delete/remove "Core::CheckUpdates();"

Once deleted, run "service tinycp restart" to reload your TinyCP and you should be good to go."

Note: I know the developer are drumming need to move to a new version but for me "Old is gold". 

Thanks.