Finding the correct CSS Selector to put in a Trigger

I am trying to add the correct CSS selector for Click Element in (Google Tag Manager)

This is for the following action:

Click on the button Subscribe.

I tried adding the class from the Thank you Message but it either doesnt trigger at all or it triggers when just opening the page.

Solution

I will propose this CSS selector

div[class*='klaviyo-form'] form button

But just wonder did you already try some CSS selector first?

Not sure why it won't work in your end.

I test it with my GTM container and looks like it's working

Here is the trigger setting