Hi @taximan63 Welcome to the Samsung Community 
some additional advice:
Firstly check that there are no issues with your Network or signal and that Mobile Data is enabled. check that your preferred sim is assigned to Messages, Settings-Connections-Sim card Manager. check thst Text is set as Default if that is preferred option, Settings - Chat Settings -Select Default Messaging Type, and set this to 'Text or Multimedia Messages'. If you go to Messages- Menu(3 dots)-Settings-More Settings-Text Messages check that a number is poulated in the Message Centre Section. sometimes there can be issues with RCS on Samsung Messages.
otherwise you may need to clear the Messages cache,Settings-Apps-Messages-Storage-clear cache. If no solution try resetting the Network connections,Settings-General Management-Reset-Reset Network Settings. could try a Soft Reset by holding down Volume Down and Power Button for around 10 seconds until the Device Reboots to see if that makes a difference, this clears memory and can solve some issues. if it is a physical sim you could try in another Device (if available) to see if the same issue ot try another sim.
If does not resolve you may need to contact your Network.
