Hello Muhammad, 

Hope you are doing well!

There is the possibility for the currency rate to not update correctly, when the invoice is been posted earlier than the date of the currency rate update. For instance, You posted the invoice on 07/01/2024 in USD with base currency LBP, but the currency rate was updated on 07/15/2024 as shown in the screenshot shared, as the invoice has the same accounting date as the invoicing date, it will not take into account the exchange rate but have the ratio of 1:1. 

To post the entries with the currency exchange rate, make sure to update the currency first, then post the invoice with the same or forthcoming dates. 

Also find attached documentation for your reference: https://www.odoo.com/documentation/17.0/applications/finance/accounting/get_started/multi_currency.html

Hope this provides clarity, 
Thank you!