The error messages do not seem to be related to the code you posted.
Let's turn your listing into a dataset.
data cntt ;
input cohort :$32. count ;
cards;
flatiron 157
trial 157
;
And then try your code.
Let's simplify things by using the modern CALL SYMPUTX() function instead of archaic CALL SYMPUT() function.
data _null_;
set cntt;
call symputx(cohort,count);
run;
Works fine.
2156 %put &=flatiron &=trial ;
FLATIRON=157 TRIAL=157
Perhaps your COHORT variable is actual numeric with a format attached? If so you might want to use the formatted value for the name name of the macro variable.
data _null_;
set cntt;
call symputx(vvalue(cohort),count);
run;