No visitor tracking since Piwik 2.11.2


I’ve noticed that Piwik hasn’t seen any visitors to my sites I allowed it to upgrade to 2.12.0 from 2.11.2 on March 24th. I subsequently upgraded to 2.13 in May but that hasn’t fixed whatever broke. I’ve followed the suggestions here: After I updated Piwik, it stopped working (blank page, widgets not loading, error message, etc.). How can I fix this? - Analytics Platform - Matomo

  1. Delete your browser cache - done
  2. Delete all files in piwik/tmp/* - done
  3. Activate the display of PHP errors in your web server configuration - none
  4. Check your web server error logs.- no Piwik related errors
  5. Reupload all Piwik files from the latest version. - done today version 2.14

…but still no joy

It shows visitor records, just nothing since March

So I checked here: Troubleshooting - Analytics Platform - Matomo
Incorrect Piwik tracking code - no, the code is correct
Make sure you are viewing reports for the correct website and date - yes
Archiving triggered from the browser must be enabled - it is
Disable all the third party plugins - all disabled, still doesn’t work
Do you have logs registered in your Piwik database? - Yes, just nothing since March
javascript enabled - yes
Tracking https (SSL) pages…- we don’t have any
Local copy of piwik.js outdated - don’t have a local copy
Using Piwik latest version - yep 2.14

The only thing on that list I haven’t checked is:
"Access to piwik.php fails If your host uses mod_security to block requests containing URLs (eg. hosts like HostGator, The Planet), check out the Piwik and mod_security FAQ. If you use HTTP Authentication (Basic or Digest) on your Piwik files, you should exclude piwik.php and piwik.js from this authentication, or visitors on your website would be prompted with the authentication popup."
I don’t know what this means or how to check it