Just this week started experiencing this issue. Talked to my daughter and she is having the same issue (same phone). When the keyboard is up for messaging or FB, the SEND button does not work. If I close the keyboard it works. I have re-started the phone and that fixes the issue. However, a couple of days later and it is happening again. I have not tried other apps, but for sure it is happening with texting and FB. Anyone else experience this and if so how did you solve it?
