Hallo and welcome from the other side of the state (West Wendover, NV/Wendover, UT).
The printer wakes itself up every few hours to do a head cleaning, so that is probably why it seemed to happen out of nowhere.
As to what I'd do about it, I would pull the cartridge in question (or all of them if it isn't specfici, seems to me my 300 says "Replace Black" or blinks for the color). You should see two copper pads, ensure that those do not have any kind of buildup on them, you should be safe to clean them with rubbing alcohol, but leave it dry for a few before putting back in. If that didn't resolve it, then I'd check the cartridge holder. Since it thinks the ink is missing, I think it'd be an electronics problem, so would check cables and connections to see if maybe something came loose.
If you do not feel safe working on your equipment, or if there is still any warranty, then I'd suggest getting a tech in. Our tech's two hours away (4 hours round trip), but luckily we only had to call once and we were covered by warranty (had to replace the old model pump). I was able to get the service manual from Roland, Fred also has it posted somewhere for contributing members on these forums, but when I called I didn't have any issue with them e-mailing it to me. It has all kinds of diagnostic and repair procedures in it, so that may be helpful as well.
Good luck on getting it solved, hopefully it's just something easy like dirty contacts
