From the TurboTax FAQ below, it seems that you can access your Expert Review at any time by using the Expert Help icon in the top right corner of the TurboTax Live screen. Here's the FAQ:
https://ttlc.intuit.com/replies/7068082
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
