My Gaggia Titanium machine says ventilate

Run about an ounce of hot water from the wand.

My Gaggia Titanium keeps reporting "FILL WATERTANK"

I received an on line solution that worked for a while being "wash out the tank in hot soapy water and dry thoroughly" as a residue forms on the tank from cold water this should help. Yes it did but now I get the message all the time and it's a hit or a miss whether the message disappears and we get our much missed cuppa! can you help?

regards