Siemens 808D milling controller

Hi Forum.
I have a CNC m/c centre with a Siemens 828D control...no problems. Just took delivery of a new mill which has come with a 808D control. I've read the book and gone through step by step but can't set tool offsets using a tool setter. Also when I start the program, I get an error saying the H number is not assigned, but I can see it is, and this program works on the 828D control. Any help appreciated. All other machines have Fanuc controls and i've never had problems like this. Any help appreciated. Geoff Australia.