I have a K2 plus with one cfs. I have been printing items with the main colour being white and a band in another colour. I have white in A, Yellow in B, Green in C and Orange in D. All Hyper PLA and identified by RFID tag being read correctly. If I choose the Yellow or Orange for the band it works fine but if I choose Green when I send to the Printer it defaults to B the Yellow even though It shows it as Green. I can select C - Green at this point and it will use C. I have removed all the filaments and re-installed them but it hasn’t changed. The Printer/CFS do show the colours correctly. I only have the K2 pus with no other devices installed. This has only happened in the past week or so. Any idea what is wrong please?
look up for auto fill settings
That is indeed a curious problem and it sounds like you’ve performed most of the diagnostics step already. On the off chance that this could be an incorrect RFID tag or faulty sensor, you said you installed and reinstalled the spools, but have you also swapped filament positions and re-synced with the slicer and verified color on the front panel? What you’re looking for is proof that when you move the filaments from one slot to another, that the RFID is registering correctly.
Another easy test is to use the RFID sensor on the side where the external spool is mounted and see what that sensor reads. It could be a case of a bad sensor in the CFS. The one on the side of the unit is a way of cross checking the filament RFID and the Sensors.
Thanks.I will try the side spool. When I take the reels out and put them back it reads the tag and shows it is Green. What I am printing will be done in a few minutes and there is little green left. I want to use Black next so I’ll put it in slot C and I‘ll see what that does.
Well it sees the Black in C and the slicer does too but that did only after I exited the slicer and the brought it back up. There was no problem when I sent it to print. It accepted C for the filament without my intervention. There looks to be more Green left than I thought so just out of curiosity after this print it done I’ll try the Green on the side spool and back in C and let you know. It will be some time tomorrow though 
This afternoon I offered the tag up to the sensor for the side spool and it read it fine. I decided that I would take out the Orange in D and put the Green in there as I had a good bit more I needed to use the Black for. The Green was recognized and I was able to do a little test print without needing to intervene. Tomorrow I will finish using the Black so I will then put the Orange back in D and try Green in C again.
Thanks for the additional data. That leads one toward suspecting a faulty RFID sensor in the CFS.
Here’s the YouTube video on how to service the board, I would first try to re-seat the connectors before replacing. Since the tutorial states there are two boards, one troubleshooting technique you may try is to swap the board and see if the problems moves to another slot:
Here’s the board replacement. What I could not find is if they have a replacement for the RFID reader (The antennae). However, I’d first verify the cabling before going the rout of replacing the board. It may not be economical to replace or you could contact creality and see if they can assist once you’ve completed your troubleshooting.
Thanks for the info. I swapped the Black out of C and took the Green from D and put it in C. Then I put the Orange back in D. So I was back to where I had been when the trouble started. So now it’s back to normal without having to force printing from C with Green. At present I don’t know what was wrong. Maybe a dodgy connection which is currently clear or perhaps one of the frequent updates has corrected the error from a recent update. If the problem arises again I’ll open up the cfs and check it all out. Thanks again for all the help.