Caffeo Varianza CSP - not drawing water

Hi,
I have had my Varianza CSP for just over 5 years of faithful service.

Today it asked to be cleaned, so I went through the normal process, put the tablet in the brew unit, put the unit back etc. The water tank then ran low and it asked to be filled.

I did this, but as I was adding the tank the machine started the draw water before the tank was fully seated and then a lot of gurgling noises ensued.

It then failed to pump any water through the system and ejected a mostly complete tablet into the coffee bin.

Since then it just goes round a loop of trying to rinse - failing - and then saying the tank needs filling and the system "needs fill" - which it fails to do.

I assume some kind of airlock has been caused when it ran out of water, but even by taking the tank off and trying to pressurise the inlet with water it still does the same.

It's a shame as it has been working flawlessly for 5 years and nearly 18,000 cups!

Any ideas?