"C" is not a valid TYPE. Only specific types are allowed and should be the same as the GTYP of the CATREF you are using.
See SPECON Reference Manual:
4.2 Selectors and Pointers for Structural Components
4.2.1 Applicability
The SPECON headings within this section may apply to components from the following list of GTYPEs:
BASE BEAM BRACe COLUmn FITTing GANTry GIRDer JOINt JOISt KNEE PILE PROFile PURLin RIDGe ROD SCTN SDRAil SPLIce STANchion STIFfener STRUt TIE
I usually make structural specs from commandline.. Specs to joints is a bit tricky, but for steel members it should be straight foreward.. new sele, new sele new spco... check out the some default specs and follow the same principle
HEADING
TYPE NAME STYP GRADE DEPTH WIDTH WEIGHT INERTIA CATREF
C */100x50x10PFC PFC 43 200 150 47 2376 /100x50x10PFC
I have to add this channel.
1) In pargon navigate to the sec you want to add the channel.
2) click the SELE one after another until you fine channel.
3) select SPCO size before the new to be added.
4) TYPE 'NEW SPCO NAME /100x50x10PFC COPY PREV'
5) While at the new SPCO query att and modify catref to /100x50x10PFC
the depth, width and weight info is already in the cata you created.