Why are my SMS texts on my Samsung S5 not being sent?

[AC Question]

All my messages were being sent fine yesterday. I installed Viber today. Would that interfere with SMS?

 

[Rukbat]

It shouldn't. Back Viber up, clear the cache, clear the data, force stop it and uninstall it. If SMS works again, it was Viber causing the problem. If not, reinstall Viber and look for another cause. (It could be that your carrier is having a problem.)