Seafile and Matomo on Raspberry Pi

I installed Seafile 7.1 on a rpi3. It works but I would like to add Web analytics tools with Matomo (since Seafile Ltd Pro is not available for armv7).
I installed Matomo successfully but I have a last configuration step: I need to find the tracking code of my seafile cloud server as explained here :

I should add the Javascript tracking code, for instance

<!-- Matomo -->
<script type="text/javascript">
  var _paq = window._paq = window._paq || [];
  /* tracker methods like "setCustomDimension" should be called before "trackPageView" */
  (function() {
    var u="//";
    _paq.push(['setTrackerUrl', u+'matomo.php']);
    _paq.push(['setSiteId', '1']);
    var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
    g.type='text/javascript'; g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s);
<!-- End Matomo Code -->

to the tag which is often defined in a ‘header.php’, ‘header.tpl’ or similar template file.

So I add this code into the file

Then on the source code of seahub pages in the head section, I can see the code I just paste. But then on Matomo interface, I still get a message that the code was not included and I have no traffic data.

Any idea why ?