WriteOff Difference Amount" nor the button Set Exchange Gain/Loss appear and could not post the payment since there is a difference

Hi
Can anyone help please
Sales Invoice amount is 10000 USD + 1500 USD for Tax, hence total Sales Invoice amount is 11500 USD

Rate is at 36 USD , I,e 1 USD =36 MUR on 01 April 2020

Sales Invoice in MUR is 414,000 MUR

Payment is processed at an Exchange rate of 40 USD, for an amount of 11500 USD, hence Paid Amount MUR is 460,000, as per Rate of 40 USD, full payment is made, however Total Allocated Amount is 11500 USD and Total Allocated Amount MUR is 414,000, the difference of 46,000, between Paid Amount of 460,000 and Total Allocated amount of 414,000 has been generated but neither the button “WriteOff Difference Amount” nor the button Set Exchange Gain/Loss appear and could not post the payment since there is a difference

Same Currency USD has been used on both Sales Invoice and Payment