Using LOOKUPVALUE for currency conversion

Anonymous , for the missing records, means blank or 0, do you have a conversion rate for that date. I doubt that at first .

The second data table might have timestamp , that can be checked by changing data type to datetime and use  format with time, there should not be any time other than 12 AM 

if that is case create a date like

Date = [datetime].date
or
Date = date(year([datetime]),month([datetime]),day([datetime]))

In power query

DateTime.Date([datetime])

Can you share a pbix after removing sensitive data.