I have just learnt that my analytics in Matomo had stopped since September 1.
I have checked with my settings and everything is intact.
And also I could not see the pages in which I have attached my code earlier.
Please suggest on what could have been the possible reasons for the aforementioned
problem.
I’d recommend you to open one of your tracked pages and open your browser’s developer tools there (F12). Then check if any errors happen on the console and if the piwik.js and piwik.php requests succeed (in the network tab).
You can also check your webservers php error log for more info.