Write him a note asking what he would like, hand him the pen & paper so he can reply? I do this for people when there is difficulty hearing, sometimes it works sometimes it doesn't, inexplicably. But it's worth a shot!

I've got some minor hearing loss, so even more difficult for me with customers like this. I'll sometimes pull a partner over whose hearing is better than mine to intercede.

Maybe show him the app if you have time, or ask him to write it in whatever language and see if you have someone that can translate ?

maybe jsut give him the same thing as last time?