A WordPress critical error means the site cannot finish loading. Visitors see a white screen or a short message about a critical error, and the pages that were taking enquiries stop. The usual cause is a plugin, a theme, or a WordPress update that ran today.
What to do in the first ten minutes
Stop pressing update. Write down the exact words on the screen, the page address, and anything that changed today: a plugin, a theme, a host email about PHP, or a new form app. If you can still open the host, do not delete files. A backup from before the error is worth more than a guess.
If the host offers a one-click restore to this morning, and you know the site was healthy this morning, that restore is a fair first move. If you are not sure, leave it and send the note.
What the repair actually is
Someone has to see which piece fails when the page loads, turn that piece off, and confirm the homepage, the form, and the editor work again. Then the piece that failed is updated, replaced, or left off on purpose. A white screen is not a reason to rebuild the whole site in the same afternoon.
If the screen is full of strange links or a page you did not write, treat it as a hack, not as a bad update. That is a different job, described in what to do when a WordPress site was hacked.
When to hire it out
If the site takes leads or payments, send the address the same day. WordPress maintenance at Uplaps starts with the broken path, not with a lecture. There is no advance. The repair is paid when that path works. If the site should move host after it is stable, that is a later migration.
Questions
What is a WordPress critical error?
It is the white screen, or the message that there has been a critical error on the site. The public pages stop, and often the editor stops too. A recent plugin, theme, or core update is the usual cause.
Should I keep updating plugins while the site is down?
No. More updates on a broken site make the cause harder to see. Stop, note what changed today, and send the address.
Do I pay before anyone looks?
No. Uplaps does not take an advance. A repair is a milestone, billed when the site answers again.