ESA failure to attend medical

I have a question I wonder if someone can help with:

I have a client who suffers with extreme anxiety and is working with mental health teams.  He had a medical for ESA in March and failed to attend for which I believe he has good cause.  His local CAB did some work with him and verbally asked ESA to be reinstated which it was but has now been stopped.  ESA now inform me that they have rejected his reasons for failure to attend and have cancelled his claim back to March but they only actioned this in June.  They were unable to offer any reason for delay.

However my question is, i have got some supportive medical evidence to properly appeal the decision re his failure to attend and plan to do this.  However as I understand he will not be paid the basic rate pending consideration of this appeal.  Is this right and should he make a new claim?  I understood he couldt make a new claim unless his condition was different or significantly worse, is this right?

Thanks