Digital BW, The Print

I received a C86 as an early Christmas present a couple of days ago. 
I am using it with a set of warm tone MIS cartridges. The system 
worked just fine for a couple of days and the prints exceeded my 
expectations. When I last turned the printer off yesterday the "cyan" 
cartridge appeared almost full on the monitor. Today, however, it all 
of a sudden reads "empty". I have only printed about 15 8.5X11 
prints, and there is obviously quite a bit of ink left in the 
cartridge (I can hear it splashing). Is there any remedy for this 
issue? Interestingly, yesterday I got an error message about the 
cartridges not being recognized. I "cancelled" and did not seem to 
have any problem after that.

Thanks in advance for your help.