I can find likely causes of your Unassigned traffic, but I need a few things first, and I will not change tags or settings until you approve.
- The rows (required): the GA4 rows where session source / medium is (not set) or the channel is Unassigned, with sessions, and total sessions for the same range. Why: I keep the two labels apart and need the share of each.
- Landing URLs (required): a sample of landing page URLs with their full query strings (for example from campaign links you share in email or social). Why: Google lists "incomplete or incorrect parameters" in UTM tags as a cause, and I check each URL for utm_source, utm_medium and utm_campaign.
- Setup (required): is Google Ads linked to this property, is auto-tagging on, and which trigger fires your Google tag in GTM. Why: Google's (not set) page lists a missing session_start (tag not on the Initialization trigger), auto-tagging off and unlinked Google Ads accounts as causes.
With these I will map each lead to the rows it could explain and give you a check list.