If a custom HTML tag fails to fire despite a correctly configured trigger, what are the most common reasons?
If a custom HTML tag fails to fire despite a correctly configured trigger, several common reasons could be the cause. The most frequent is JavaScript errors within the custom HTML tag code. Even a small syntax error can prevent the tag from executing. Use the browser's developer console to check for JavaScript errors. The code might be relying on elements that are not yet available in the DOM (Document Object Model) when the tag fires. This is particularly common with dynamically loaded content. Use a 'DOM Ready' or 'Window Loaded' trigger, or implement a delay using `setTimeout()` to ensure the elements are present. Another reason is Content Security Policy (CSP) restrictions. CSP is a security mechanism that controls the resources a browser is allowed to load. If the custom HTML tag attempts to load resources from a domain not whitelisted in the CSP, the tag will be blocked. Check the browser's developer console for CSP errors. A blocking trigger might also be preventing the tag from firing. A blocking trigger (trigger exception) prevents a tag from firing when certain conditions are met. If a blocking trigger is active, it could be overriding the firing trigger. The tag might be paused or disabled. In the GTM interface, ensure that the tag is enabled and has not been accidentally paused. The GTM container snippet might not be correctly installed on the page. Verify that the GTM container snippet is present and correctly placed in the `<head>` section of the page. The custom HTML tag might be interfering with other tags or scripts on the page. Use the GTM preview mode to inspect the tag firing sequence and identify any conflicts. The tag might be firing but not producing the expected result. For example, if the tag is supposed to modify the DOM, the changes might not be visible due to CSS styles or other factors. Use the browser's developer tools to inspect the page and verify that the tag is producing the desired effect. Finally, consider asynchronous script loading. If the custom HTML tag includes external scripts that are loaded asynchronously, they might not be fully loaded and executed before the tag completes. Use a callback function or a promise to ensure the scripts are fully loaded before proceeding.