Messages not sending

What you see	What it means	What to do
A clock	Waiting to send.	Check your connection. It sends by itself.
A red alert	It couldn't be sent.	Tap the message to try again.
One tick that stays	Sent, but not delivered yet.	Their phone may be off or offline. It's delivered when they reconnect.

Other reasons

You blocked them, or they blocked you. You can't message each other while blocked.
Only admins can send messages in that group.
You're no longer in the group: you left, or were removed.
The file is too large. Attachments can be up to 100 MB.
Your storage is full (the app stops until you free space). See Storage full.
Slow mode or another rule in a ZapRooms channel.