Before touching a single setting, confirm the drop is even real. The first move is not a fix at all; it is verification, because the most common cause of a traffic chart falling off a cliff is a tracking problem or a seasonal pattern, and reaching for a repair before you know what broke can make a non-problem worse. Verification first, scope second, repair third, in that order.
Verification means checking the drop in more than one place. If analytics shows a fall but Search Console does not, or the other way round, you are likely looking at a measurement issue rather than lost visibility. Comparing the same period against last year separates a genuine decline from a predictable seasonal dip. Only once the drop survives that check does it earn an investigation.
Scope is the step that routes everything after it. Establish whether the loss is site-wide or limited to certain pages, because the two point in opposite directions. A site-wide fall tends toward algorithmic, technical, or domain-level causes: a sweeping block, a server returning errors, a sitewide demotion. A drop confined to particular pages tends toward content, cannibalization, or a competitor overtaking you. Mixing these up leads to applying a global fix to a local problem, or the reverse.
When you do act, you fix the highest-leverage cause rather than the easiest one. Check the Security and Manual Actions report first, since a manual action or hacked-site flag is often the single thing behind a catastrophic fall and overrides everything else. After that, index coverage: an accidental noindex, a robots block, a run of server errors. The tempting small fix, adjusting speed or schema, is almost never the answer to a sudden drop.
So the reader runs the scope-and-confirm steps in full before changing anything, letting the diagnosis decide the first repair instead of guessing at it.