Application not recognizing String Rate table

Hi ,

I have developed a simple scenario calculation of commission based on Department.\

Raisd a manual transaction with commission_headers.attribute27 as ''back end sales''

Below is the rate table

=================

back end sales - 15

front End sales :85

formulae

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ip exp : commission_headers.attribute27(department name)

op expression

-----------------

Rate table result

Expected result should commission amount should give me as 15 ,but it's printing Zero

Rate tier id in commission lines table is -1

is it application issue is there any patch required ..kindly advise

Regards,

PG