Not sure if this is a Preview or a MODX issue, but after updating a site to MODX 3.1.0 and Preview to 1.4.1, the preview button has gone missing. I reinstalled Preview but no change.
Additionally, the regular View button gets turned into nothing but an arrow, which is very confusing for my clients. They don't know what it means. Reverting to Preview 1.3.0 restores the View button to text, but the Preview button still does not appear.