If you have added the code snippet to your page, then check your Sampling settings that define if there's a delay before displaying the survey or how long to wait between displaying a survey to a returning visitor.

If you used the default settings, it will show a survey to a returning visitor every 30days. This means that if you're testing your survey, you'll see it the first time you visit your website and you will only see it again after 30days. For testing, you might want to change the sample rate!

If you want to show a survey immediately a visitor lands on the page, change your Sampling settings to First Survey Shown = 0.00