First check whether MailerPlex is installed correctly. Follow the steps below to check.
Check for the MailerPlex logo on your Gmail toolbar. If you can’t find the logo within 1 minute after loading Gmail, the extension may not have been installed properly. Please uninstall using the instruction below and reinstall from the Chrome Store.
Click on Compose button inside Gmail. Check whether you are getting MailerPlex logo in your compose box just after the Send button. If you are not getting the icon, you need to uninstall and re-install MailerPlex extension from the chrome store.
If both of the above steps are fine, then MailerPlex has been installed correctly. You can try sending emails to multiple recipients and check for the activities. If you are sending email to yourself, you must open that email in a different browser (Edge, Firefox, Safari or a mobile) to test activities. Opening in the same browser where you have installed the extension does not generate any event. We have put that check in place to make sure that self-opens or false-opens (you opening your own mail) don’t get tracked. See this article for more details - Emails sent to myself are not being tracked
How To Uninstall MailerPlex Extension From Chrome
To uninstall MailerPlex extension follow the instruction from this page How to uninstall and reinstall MailerPlex