""We're sorry to hear about..." is another of those phrases like "we take.....very seriously". It's just rolled out without thinking and almost certainly without intending it to mean anything.
Nevertheless it strikes the ear as indicating that the query was the first they'd heard about the problem but this belies the present tense in "we're doing all we can" which implies ongoing action. If they've only just heard the only thing they can be doing at the time is looking at what action they can take.
It would make more sense if they said they were aware of it and were doing all they could or if they said they were sorry to hear about it and will examine the problem (preferably urgently). As it is this bit of boilerplate is about as unreassuring as they could be short of simply coming out and saying what they really mean which is probably along the lines of "So what do you expect us to do about it?".