Raster to Ascii - 'No VIsible Layers'

I am trying to convert a few raster layers into ascii so that I can use the MCDM tool in Idrisi. The 'raster to ascii' tool appears to create the appropriate ascii files. However, when I import these into Idrisi the layer is blank with a header stating 'No visible layers'.

I am not sure why this is occurring or what I need to chnage to make the data appear. The files should be a 'distance from ...' file.

Hope you can help

Joss

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