Texting troubleshooting

Before the last update to the OS system I was able to receive and send text from either iMessage users or SMS. Now I only receive messages on my devices when it is users of iMessage and I am no longer able to write text to non iMessage users. I even attempted to reply to a message that was already in my box and it shows me that it can't be delivered although I had already had a conversation going for the past few days using my computer. What happened and how can I resync?