I have figured some things out after a lot of experimentation. If you have no other windows maximised (i.e. everything except Word is minimised down), if you have no text in the document after the cursor, if you have recently saved the document
and if the whole line is completely visible (i.e. it's not half cut off at the bottom of the screen), then it will work! If your autotext entries aren't suggested, try minimising everything else and save your document. Then it might work - until the next time
it mysteriously decides to stop. This IS a bug in Word and it should be fixed by the Microsoft people!
Sorry, I don't concur. The activity you observed may well have to do with where the AutoText is stored on your system. Check for the following behavior.
AutoText must be stored in a template. It can be stored in the normal template; that is the default location for storage. It can also be stored in the attached document template. Finally, it can be stored in other loaded global templates including Building
Blocks.dotx or Built-In Building Blocks.dotx.
Tooltips display for AutoText in Word 2003 for any available AutoText.
They do not display in Word 2007.
They display in 2010 if the holder of the AutoText is normal.dotm or the attached template.
In all three versions of the program the AutoText is inserted if you type at least 4 characters of the entry name (and those characters are unique) and then press F3.
On my system at least, minimizing windows or saving the recipient document have nothing to do with whether Tooltips for AutoText entries appear.