dbms_lob.instr comparison incorrect

the code

(select dbms_lob.substr(col1,40,11) from
tbl1
where trunc(col2)=‘27 Jun 2016’
and col3= 'User ’ and dbms_lob.instr(col1,'Applicant ') >0 ) as string

does not return any value even if the instr function returns rows which are >0.

Could you please suggest where query is wrong