Failure to attend WCA - any caselaw?

Hello

I met a gentleman with severe and enduring poor mental health yesterday. In addition to his poor health, English is his second language.
He is appealing a decision to end his ESA because he has failed to attend 4 WCA’s.
He has a new claim up and running - worsening condition. The appeal will be a time limited one of roughly 3/4 months.

Is anyone familiar with any caselaw regarding failiure to attend? Evidence available to prove his condition is severe. Initial decision made November 12.

Many thanks in advance.

Yasmin