Messaging, why can't I get trash can to show when I wish to delete a message?
Welcome to iMore! I have that problem some too. It's been a hit or miss thing. I don't really know how to fix it. It just sometimes is there and sometimes not. But it did seem to help when I deleted all the 3rd party keyboards. I did that as a test. It seemed to work. But I got my keyboards back. And it does show sometimes. There's a trick to it I can't recall. It seems to help also to turn the predictive feature off. I'll play with it some more and find the trick. Apple should fix this.
You might also try deleting the messages app from the App Switcher. Or swipe out the background messsges app. See if that helps.
Sent from my ancient but trustworthy iPhone 5.