Here's the link to the section you needed in the training portal: https://dovetailmktg.kartra.com/portal/mgsitlogin/subcategory/123
This is almost always a case of your Zap (in Zapier) being turned off.
Simply find your Zap in Zapier and turn it back on (the 'light switch' should be all the way to the right and green colored.)
After you do that I would recommend doing a 'fake test lead' to ensure they are actually going into Zapier. Be sure to give it a few minutes after the test before you determine it's still not working. Sometimes its not completely instantaneous. (Don't forget that if you have a 'overnight hold delay' setup and you're doing this late at night, you may not see the lead go in because it's being held or delayed).
If that still doesn't fix it, then you likely have Zapier setup incorrectly. Go back to Module 4, to the Connecting Accounts With Zapier section and double check your Zapier setup.