R3000, VLM blank on nozzle check

Hi everyone, first pose, here goes: VLM suddenly not showing on nozzle check of R3000. As I understand it, the solution procedure is to get a blank cartridge and fill with the pink stuff. Install and leave for a day or two. Do a head cleaning cycle and a nozzle check and if it’s ok, the pink stuff should show up on the nozzle check.
Is this correct ?, if yes, what next, do I remove the cartridge and replace with VLM cartridge and carry on as normal.

Any help much appreciated.