Nothing, at first. That is exactly the problem. A neglected website does not fail on a Tuesday with a warning email — it degrades quietly for months and then breaks at the worst possible moment, usually while you are asleep or on holiday.
Here is the pattern we see on almost every site that comes to us after a year without care:
Month 1–3
Plugin and theme updates start stacking up. Nothing visible yet, but the gap between your site and current versions is widening.
Month 4–6
A plugin conflict breaks a contact form. Enquiries stop arriving and nobody notices, because a form that fails silently looks exactly like a quiet week.
Month 7–9
Page speed has crept up as images and plugins accumulate. Rankings slip, and the mobile experience is now measurably worse than your competitors.
Month 10–12
An unpatched plugin vulnerability gets exploited. Now you are paying for emergency malware cleanup instead of maintenance — usually several times the annual plan cost.
Every stage above is cheaper to prevent than to fix. That is the entire argument for monthly website maintenance, and it is why our plans are priced well below what a single emergency recovery costs.