Okuma Mill 511V Z-axis needs zeroing

[lfacio12]

Hi,
I need help in getting the correct procedure to reference the z-axis for an Okuma & Howa 511V Mill. This alarm (300 Z-axis needs zeroing) came up after the batteries that hold the zero reference died and the machine was turned off. I would really appreciate the help.

Thanks

[Algirdas]

Would you tell us, what a control of this machine is? Please.