Well It depends on the printer model and the cartridges you are refilling as it may or may not be a refillable cartridge.
For Instance - Canon PGI-250 / CLI-251 Cartridges are refillable that comes with auto resetted chips on the cartridges meaning it will show full after you refill them whereas on the other hand Canon PGI-280 / CLI-281 cartridges are "Not" refillable as they have one time use chips.
For Refillable cartridges -
> Please make sure there is no ink spilled on the chip nor any debris on it or in the cartridge slot inside the printer as should be clean.
> Refill before the cartridge is completely out of ink to avoid any issues and can refill when 1/4 empty.