If you get the "FR2849" error on your Creality CFS or if it has trouble pushing the filament past the CFS hub then it might be that the filament sensor in the hub is faulty. To check if this is the case you have to dismantle the CFS hub and gain access to the sensor PCB.
To do this, please follow the reference images below:
Unscrew the screws marked with red.
Once you have gained access to the inside of the CFS hub, turn the CFS/printer on with power, unload all filament from the CFS, verify that no filament is stuck in the hub, and then check if any of the 4 LEDs are turned ON even with no filament loaded.
If any of the 4 LEDs are still turned ON even with no filament loaded and no filament residue then the CFS hub filament sensor is most likely faulty, contact the supplier you bought the printer/CFS from for further support or replace the sensor if you can buy it or already have it in stock.