How to use CallMeBot Signal API:
https://signal.callmebot.com/signal/send.php?phone=your phone number&apikey=apikey&text=Text to send (to send a Signal Message to yourself)
apikey = The apikey that you received during authentication
For more information visit https://www.callmebot.com/blog/free-api-signal-messaging/.
APIKey is invalid.
Please ensure that the apikey is correct or request a new one.
Instructions here:
https://www.callmebot.com/blog/free-api-signal-messaging/