Hello, can you give us more information? How did you contact them the first time? It might be that the message didn't get through to them. So it might be an idea to start by writing:
"Hello, I tried to contact you on <DATE>, but am not sure if my message got through. Please can you let me know if you received it. I'm copying it here again, in case you didn't get it. Please can you let me know ..."