Make the client feel welcome. Starting a conversation may be hard at first but remind them that you are available to provide as much support as possible.
If they are willing to describe how they are feeling upon contact, then simply assure them that you are there to listen. You do not have to offer advice, listening is more than enough.
Reassure them that you will work at their pace and that there is no pressure involved. Allow them to tell you what their expectations may be.
Because of the low levels of interest in activities at this point, you can help them set small goals. Remind them that it is about the small wins. Work together to create a schedule based on what they can achieve, one goal at a time.