Update released today fixed it. Thank You!!
Its not saying I have any updates in the WordPress admin
I’m not using the TinyMCE Advanced Plugin. I did an experiment with a clean WP Install that was on version 3.83. Installed ACF, Wysiwyg display HTML button. Updated to 3.9 HTML button disappeared
The Wysiwyg editor field is working for me minus the missing HTML button. Which I really need!!