Bison is always giving me a yyerror and yyparse() is always returning 1

Question

I am constantly getting yyerror : syntax error no matter the input file and yyparse() is always returning 1. I am having trouble finding what the issue is. I believe my BNF and input should be correct but I just keep getting this error and its driving me crazy.

%{
#include <stdio.h>
int yylex(void);
int yyerror(char *);
%}
%token LEFTPAREN RIGHTPAREN ASSIGNMENT SEMICOLON IF THEN ELSE BEGIN END WHILE
%token DO PROGRAM VAR AS INT BOOL WRITEINT READINT NUMBER LITERAL
%token OP2 OP3 OP4 IDENTIFIER
%start program
%%
program : PROGRAM declerations BEGIN statementSequence END
;
declerations : VAR IDENTIFIER AS type SEMICOLON declerations |
;
type : INT | BOOL
;
statementSequence : statement SEMICOLON statementSequence |
;
statement : assignment | ifStatement | whileStatement | writeInt
;
assignment : IDENTIFIER ASSIGNMENT expression | IDENTIFIER ASSIGNMENT READINT
;
ifStatement : IF expression THEN statementSequence elseClause END
;
elseClause : ELSE statementSequence |
;
whileStatement : WHILE expression DO statementSequence END
;
writeInt : WRITEINT expression
;
expression : simpleExpression | simpleExpression OP4 simpleExpression
;
simpleExpression : term OP3 term | term
;
term : factor OP2 factor | factor
;
factor : IDENTIFIER | NUMBER | LITERAL | LEFTPAREN expression RIGHTPAREN
;
%%
int yyerror(char *s) {
  printf("yyerror : %s\n",s);
}
int main(){
  printf("%d\n", yyparse());
  return 0;
}