The American, 24, has not competed since last week's team final, where she performed on vault but no other apparatus before saying she wanted to protect her mental health.
The pre-Games favourite, a four-time Olympic champion, has been suffering with the 'twisties', which gymnasts describe as a kind of mental block.
Biles won bronze on the beam at Rio 2016.
The American had arrived in Tokyo with a chance of six gold medals, and such has been her dominance of her sport that they were all realistic.
