@Vampire47: Are you using the stock Messages app that came preinstalled on your Galaxy S9? Do you have an active network SIM inserted in the device? Are you still able to make and receive calls, and receive messages?
To troubleshoot the issue, please try heading to Settings > Connections > SIM card manager, and make sure your SIM is toggled on, and it is assigned to Text Messages via the 'Preferred SIM cards' options below.
