Tracking code not available, Test script 2 empty result, Piwik 2.8.3

Just started trying to use this plugin. Sounds like exactly what I need.

I saw another support topic that looked very similar, but that was for an older version of Piwik and I think the bug that caused it has been fixed in a more recent version. I’m using the latest version of Piwik.

Also, note that although the first test script succeeds and shows the correct site ID, both the Piwik dashboard and the “Support > Get site configuration details” show the site ID as 1 (which is incorrect).

Here’s the error message:
<!-- WP-Piwik ERROR: Tracking code not availbale -->

And here’s the output from the second (failing) test script:

*** Test 2/2: SitesManager.getSitesIdFromSiteUrl ***
Using: cURL
SSL peer verification: enabled
User Agent:
Call: http://my.piwik.server.url/?module=API&method=SitesManager.getSitesIdFromSiteUrl&url=http%3A%2F%2Fmy.wordpress.site.url&format=XML&token_auth= + TOKEN
Result:
HTTP/1.1 200 OK
Server: nginx
Date: Fri, 31 Oct 2014 14:23:27 GMT
Content-Type: text/xml; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
Vary: Accept-Encoding

<?xml version="1.0" encoding="utf-8" ?>
<result />
Time: 0.51s

https://ww.wp.xz.cn/plugins/wp-piwik/