What does it mean if the member have concern of reavailment in the hearing.
It means you need a lawyer.
Reavailement typically involves renewing your home country passport and/or traveling to your home country while also claiming that you are being persecuted. For example, if you traveled a few times outside of your home country during the period you have claimed you were being persecuted and then returned back to your home country, and then later flew to Canada and claimed asylum here, that would be a problem.
Impossible to really comment what's triggering this concern without knowing the full details of your case. However get a lawyer if you're not already working with one.