Good day

I have a CNC Lathe with a GSK 928 TD-L system.
The machine has not been powered up since August last year 2023.

When powering up the machine i get the following error on the HMI:

X encoder cell failure
Reset encoder (terminate Er-49) - (REW)
Exit-- (Enter)

The AC servo motor drive unit details are:
GSK DA98C series
The error on the drive is Er.-46 and the other drive is Er.-49

Can anyone help with the following info:

What do the errors mean?
How to I rectify the problem?

Thank you