Brummie

Hi, A year ago I bought a 45' narrow boat that had been stored and unattended at a marina for two years due to previous owners illness. I moved the boat to a marina nearer my home about ten mile trip just as the lockdown started. The boat has a macerator toilet with a plastic holding tank, on inspection I found the tank is just over half full (yuk). As this has now been stood for two plus years do you think it would still be liquid enough to pump out or would it have solidified. should I top the tank up with water and leave for a short while, any suggestions please.