This happens when your personalized links contain whitespaces or double quotes. These characters prevent click tracking in YAMM when used in spreadsheet-based URLs.
Encode your query parameters with the ENCODEURL() function as described on this page.
❌ Incorrect (with spaces or unencoded quotes — tracking fails)https://example.com/?productid="Yet Another Mail Merge"
✅ Correct (encoded — tracking works)
https://example.com/?productid=%22Yet%20Another%20Mail%20Merge%22
warning Avoid using ENCODEURL for the entire URL
Use ENCODEURL to encode query parameters, but not full URLs. It also encodes slashes (/) and colons (:) in the base URL (https://), which breaks the link.