Pixels, containers and properties are owned by individual accounts. When the freelancer who built them moves on, or the last agency does, you inherit tracking you can read but cannot change. The failure arrives the day something breaks.
React, Vue, Next.js and modern Shopify themes swap content without reloading the document. Tags wired to page loads fire once on arrival and then go silent, which is why a thank you page conversion can be perfectly configured and still never fire for a real user.
A single dropdown on each conversion action decides whether repeat conversions from the same click all count. Lead gen accounts set to Every report numbers the CRM cannot match, and the bidding algorithm learns from the inflation.
One checkbox in Google Ads decides whether every ad click carries an identifier. Turned off, nothing errors and nothing turns red. Your paid traffic quietly starts showing up as organic, your offline conversion imports stop working, and bidding loses the thread.