Galaxy S7 not capitalizing first word in sentence - text message

Settings/ General management/ Language and input/ Virtual keyboard/ Select the one you use/ Turn on Auto capitalize.

that worked for about two text messages, but then it went back... just as this comment did. It worked fine until a couple of months ago when it started adding a space before the first word, so that auto - capitalizing doesn't apply, because it doesn't think it's the first word of a sentence. Something changed. Hopefully they will fix this!

You may try a different keyboard. Gboard from Google is available at play store.