First, please always (and also) look at the CHANGELOG.md. It will tell you more about the changes made.
There is a new way to register the plugin.
Before it was just this file in the support/index.js file
import 'cypress-testrail';The new way requires the plugin to be registered in the plugins/index.js file.
This is required, because we need new events to read data about browsers and specs, and that is only available in that scope.
const TestRailReporter = require('cypress-testrail');
module.exports = (on, config) => {
new TestRailReporter(on, config).register();
return config
}That's it, it should all work again!