Someone out there has a simple answer for this, I just can't find it.

I have a Boehringer VDF 180 lathe with a Siemens 840D control. It was crashed and minor repairs were needed (shear bolts) but now it is asking me to reference the z axis again. This machine normally does not need to be referenced on startup nor does this error effect the machine in any way, it sill works perfectly. The manual I have asks for buttons that do not exist on my control as it is more for a milling machine.

The error is 700941: Z axis please reference again

Again, the machine works fine but the constant flashing error is a bit annoying. Any help appreciated! Thanks!