epson 2400 communication error
I believe this may (others chime in) be the indication that your waste ink tank/pad is full which is not user replaceable.
Just as a tip, the rule of thumb is alternating flashing lights for paper and ink. If those lights are flashing together it's a "General Error" rather than a "Service Required" one. The former is often down to paper jams, chip issues or electronics failure, while the latter is indeed a waste counter problem and much easier to solve.
You can reset the waste counter and pray but (and bear in mind I'm biased here) you are risking an overflow of the pads, especially if you are using non-OEM and have experienced any leaky cartridges, overpressured CIS systems, etc... So thinking about an external waste ink tank might be in order.
As for resources my non-commercial blog on wasteink.co.uk is a good option too.. The commercial ones are easy enough to locate if you dig around too.