Common Causes

Google Analytics DebugView requires the debug_mode parameter to be active in GA4 requests for events to appear, which GTM Preview mode should automatically add, but several issues can prevent this from reaching DebugView. In WordPress setups with GTM, logging into the admin panel often blocks debug events entirely—log out completely and test again, as this resolves the issue for many users. Browser extensions (ad blockers, privacy tools), cached data, or developer tools blocking requests to google-analytics.com or gtm.js can also stop data flow despite GTM showing tags firing.

Key Troubleshooting Steps

• Verify debug parameter: Open browser DevTools > Network tab, filter for collect?v=2, and check recent GA4 requests for dbg or ep.debug_mode=true. If missing, confirm GTM Preview connects properly.

• Check GA4 filters: In GA4 Admin > Data Settings > Data Filters, temporarily set "Internal traffic" to Testing (it blocks DebugView even with Developer filter active).

• Clear interferences: Disable all extensions, clear cache/cookies, use incognito mode or another browser (avoid Brave), and ensure no ga-disable-XXXXXX code exists in page source.

• WordPress-specific: Clear site cache, check for plugin conflicts (e.g., avoid duplicate GA via plugins like Site Kit alongside GTM), and confirm no legacy Universal Analytics tags remain—remove them and use GA4 config via GTM.

Additional Checks

Ensure you're viewing the correct GA4 property (match Measurement ID from GTM/site to Admin > Data Streams) and the right device in DebugView's dropdown, even if it shows "No devices". Consent mode or privacy controls might limit events if not consented; test without them. Delays or bugs can occur—wait 10-60 minutes or restart browser fully. If issues persist, share your GA4 Measurement ID, GTM Preview console screenshots, and Network tab details for collect requests.