I have been testing Piwik on a dedicated server since May 2012. I run WordPress sites on THAT server and on several other hosting accounts.
To date I have had complete success using the WP-Piwik plugin on all the WordPress installations on the dedicated server where the Piwik is installed.
I have a hosting account with Bluehost (and a second with Gray Webhost, which is a Bluehost reseller). About a month ago the WP-Piwik plugin for 2 very low-traffic Websites running at Gray Webhost stopped working. The Gray Webhost support team worked with me for 2-3 days to confirm that they and Bluehost were NOT in any way blocking the communication between the plugin and the server. No security settings had been changed either in my account or at the hosting level.
After collecting data for several weeks the plugins for both sites on Gray Webhost simply STOPPED communicating with the Piwik server on my dedicated server.
Now over the past few days the same problem has cropped up with the Bluehost account. I have five-six low-to-moderate traffic WordPress installations there and all have suddenly stopped communicating with the dedicated server.
In neither case had I made any changes to any sites, EXCEPT that I normally update plugins and themes whenever I see that updates are available. Of course, I do this for the installations on the dedicated server as well.
Nearly all sites are configured as WordPress Networks using subdomains. However, I have 1 installation on Bluehost that is NOT configured as network and its plugin has stopped working AND I have 1 installation on the dedicated server and its plugin still works.
I have a FOURTH hosting account with ZZ Hosting. They, like Bluehost, use cPanel. I have several low-traffic WordPress sites installed there as well. All of them are using the WP-Piwik plugin and all of them are still working fine. I even updated two themes on one of those installations before posting this message and so far the WP-Piwik plugin is still working.
When the plugin stops working regardless of whether it's on a network or single installation I get the following error: "An error occured: Piwik did not answer. Please check your entered Piwik URL."
My server is NOT suddenly blocking the Bluehost IP address. I control that and I have not blocked that IP address. In fact, I can use another script to connect to the dedicated server just fine.
I have scanned dozens of WP-Piwik and Piwik support discussions here, at Piwik.Org, and on other forums. These problems are periodically reported going back at least a year. A few people appear to report success in restoring connectivity but most of the error reports are unresolved (or abandoned).
My dedicated server has been subjected to some brute force hack attempts over the past few months. I have been blocking the proxy IP addresses aggressively through the Linux firewall. The hosting ISP for the dedicated server assures me I have taken all prudent measures to fight off the hackers. The latest WP-Piwik failure does not coincide with any hack attempts. The dedicated server is running fine.
I originally used the same authorization on all the sites. When this problem first began I created a couple of Piwik user accounts and embedded their authorization codes in a few sites. That makes no difference.
The Piwik is up-to-date (version 1.8.3), the WP-Piwik is up-to-date (version 0.96), the WordPress is up-to-date (version 3.4.1). On the Bluehost account I switched the PHP from 5.2 to 5.4 (single php.ini) and that made no difference.
I have deleted all plugins and reinstalled. I have deleted all plugins and just installed WP-Piwik. Makes no difference.
I cannot find anything in the error logs that points to an issue.
Does anyone know why Bluehost-based WP-Piwik plugins may suddenly stop communicating with the server? I gave up on Google Analytics in April because it can no longer block crawlers from inflating statistics. Piwik seems to do a much better job of filtering out robots. I really hope there is a simple explanation/solution for all this. Unfortunately I just cannot find it.