Confirm the drop is real
Compare like-for-like periods, weekdays and time zones. Exclude incomplete days and check whether consent, tags, internal filters or reporting definitions changed. Losing bot or irrelevant traffic can reduce sessions without reducing business.
Compare analytics with Search Console for organic clicks and platform clicks for paid traffic. These systems measure different things, so expect differences in totals. A sharp analytics-only fall after a tag release is a reason to inspect measurement, not to rewrite every page.
Look for evidenceAsk whether enquiries, orders and independent click records fell at the same time.