The problem with my WP Blipper Widget was so frustrating and incomprehensible to me that I asked Digital Ocean for help. I opened a support ticket, and detailed my woes.
Chris B got right back to me. He suspected a missing PHP package somewhere. He gave me a way to diagnose the problem: stick these lines of code in my source file:
error_reporting(-1); ini_set('display_errors', 'On');
This generated the following error:
Fatal error: Call to undefined function wpbw_Blipfoto\wpbw_Api\curl_init() in/var/www/html/wp-content/plugins/wp-blipper-widget/includes/Blipfoto/Api/Request.php on line 130.
So I was missing the cURL library thing. I had no idea how to install it. Probably some sort of sudo apt-get affair. I had a google, then emailed Chris back. He told me I could install cURL by using the following:
sudo apt-get install -y curl php5-curl
(I was right: it was some sort of sudo apt-get affair.)
He said I might have to restart apache, and gave me the command for that, too:
sudo service apache2 restart
I did those things (luckily I’d got the SSH key up-and-running previously, so that was no bother), then I reloaded my web page. It only worked! I am delighted.
I recommend Digital Ocean for web hosting based on my experience so far.