Convert Unit workspace returning flat spectrum

Hello, I have written a simple script that extracts monitor information from a workspace and creates a new workspace. I want to convert the units from time to wavelength but when I run the script I get a flat spectrum NormalisedSpectrumWavelength-1
Bellow is a copy of the script I am using.

Spectrum=Load("\\\\isis\\inst$\\NDXALF\\Instrument\\data\\cycle_19_1\\ALF79970.raw")
ExtractMonitors(Spectrum,MonitorWorkspace='Monitors')

Monitors=mtd['Monitors']

MonitorX=Monitors.readX(0)
MonitorY=Monitors.readY(0)
MonitorE=Monitors.readE(0)

Monitor=CreateWorkspace(MonitorX,MonitorY,MonitorE,UnitX='TOF',ParentWorkspace=Monitors)
NormalisedSpectrum=NormaliseByCurrent(Monitor)
NormalisedSpectrumWavelength=ConvertUnits(NormalisedSpectrum,Target='Wavelength')

Has anyone run into this problem before, I was hoping that by setting the Parent workspace my problem would be solved as the new workspace should have all the same log and instrument information.

Does ConvertUnits() before give you the result you want?

Spectrum=Load("\\\\isis\\inst$\\NDXALF\\Instrument\\data\\cycle_19_1\\ALF79970.raw")
ExtractMonitors(Spectrum,MonitorWorkspace='Monitors')
SpecW = ConvertUnits(Spectrum,Target='Wavelength')
Monitors=mtd['Monitors']
MonW=ConvertUnits(Monitors,Target='Wavelength')

MonitorX=MonW.readX(0)
MonitorY=MonW.readY(0)
MonitorE=MonW.readE(0)

Monitor=CreateWorkspace(MonitorX,MonitorY,MonitorE,UnitX='Wavelength',ParentWorkspace=MonW)
NormalisedSpectrum=NormaliseByCurrent(Monitor)

Then plot the “NormalisedSpectrum” Workspace