Troubleshooting

I can't reply: the window has closed

Why the reply box is locked after 24 hours and how to reach the person anyway.

WhatsApp only lets you send a free message within 24 hours of the person's last message. After that, the chat header shows Reply window closed. The reply box says "You can reply when they message again. WhatsApp allows replies only within 24 hours of their last message." This is a WhatsApp rule, not a fault. The assistant follows it too.

Check these first

Wait for them to write

Who can fix it: nobody needs to. As soon as the person sends any message, the window opens for another 24 hours and you can reply.

Reach them with a broadcast

Who can fix it: you or an admin. A broadcast can use an approved template, and templates are allowed outside the window.

Go to Broadcasts and start a new one.
Choose just this person, or their group.
Pick an approved template and send.

See Send a broadcast. If there is no suitable template, an admin can prepare one: see Prepare a template.

Ask for a follow-up

Who can fix it: you. Add a task or follow-up so you remember to contact them once they write again. See Follow-ups.

A message failed with this reason

If a message shows "The 24-hour reply window had closed, so WhatsApp would not accept it.", it was sent too late. Try again will not work. Use a template broadcast instead. See A message wasn't delivered.

Tip: You can see when the window closes at the top of an open chat. Reply before then if the matter is important.

Still stuck?

Select Help at the bottom right to ask the help assistant. It can check your setup and send a support request to your admins.