Matomo Wordpress broke after HTTPS migration

Hi there,

SOLVED, but not Understood.
On 10.February, I followed this procedure for upgrading the site from http to https:

On 7.June or thereabouts, the piwik tracking code stopped working.
I just tried to change the plugin settings to the path https instead of http and now it is working. Yay!
But why the delay in breaking?

HERE’s THE ORIGINAL POST

I’ve been using self-hosted piwik since 2012.

Some months ago the plugin stopped showing any data within wordpress, but tracking was still working and data viewable at https:// tangoforge.com/piwik.

In trying to track down problem with the plugin about two weeks ago, I did notice this error in the plugin configuration page, but tracking was still working at that point.
“WP-Matomo 1.0.21 was not able to connect to Matomo using your configuration. Check the »Connect to Matomo« section below.” I asked for help with the plugin on wordpress forums. Have received no response there.

Checking back a few days later I realized that tracking also stopped working.

Trying to follow the instructions above, using firefox I opened Developer Tools and clicked network and then filtered for piwik and nothing appears.

How should I fix it?

Thank you for your help!