I'm using phenix cryo-EM real-space refinement for one of my cryo-em models which contains a ligand called spirilloxanthin, a very common carotenoid molecule found in nature. Its code is CRT which can be found in wwPDB ligand dictionary and in COOT. However, when I run real-space refinement, I got a error message caused by this ligand "Fatal problem interpreting model file: Number of atoms with unknot non bonded type symbols: xxx please edit the model file to resolve the problem and /or supply a cis file with matching restrain definitions, along with apply_cif_modification and apply-cis-link parameter definitions if necessary". I checked my pdb file. All atom names and order are exactly same as that in wwPDB. I also try to insert it into map using COOT monomer find method. It does not work as well. It seems to me that Phenix can not recognise this ligand, CRT spirilloxanthin. Does anyone have an idea of how to deal with this issue. Or is it OK if I add CRT.cif into upload window of Phenix for refinement? Any suggestion is greatly appreciated. 

The version of Phenix I am using is Mac version recently downloaded from Phenix website. 

Best regards