everyone I am new here and I need some help. I keep encountering this error:

 proc surveylogistic data=nhis29;
 cluster ppsu;
 strata pstrat;
 weight wtfa;
 class SRVY_YR(ref='2021') edu(ref='1') pov(ref='1') sex(ref='1')/param=ref;
 model ft=srvy_yr edu pov sex/expb;
 run;

ERROR: Invalid reference value for SRVY_YR.

Yet for the same variable and reference everything seems fine as shown below:

 proc surveylogistic data=nhis29;
 cluster ppsu;
 strata pstrat;
 weight wtfa;
 class SRVY_YR(ref='2021')/param=ref;
 model ft(event='1')=srvy_yr/expb;
 run;

NOTE: PROC SURVEYLOGISTIC is modeling the probability that ft=1.
NOTE: Convergence criterion (GCONV=1E-8) satisfied.
NOTE: PROCEDURE SURVEYLOGISTIC used (Total process time):
real time 0.20 seconds
cpu time 0.11 seconds

I can’t think of what I missed, and any assistance would be appreciated

I tried proc surveyfreq and 2021 is a category and works fine