When looking at the team tab in a time report (Reports > Time), the billable amount column is removed if any team members have tracked time to more than one currency. Harvest does not do any currency conversions, so since we're unable to correctly display a billable amount as a single currency, the billable amount column is eliminated for the team tab in this report. 
 
You can export a detailed time report (Reports > Detailed time) in CSV or Excel format for the time period and view the Currency column to see which entries are in different currencies. 
 
You will still see multiple currencies displayed at the top of the time report in the summary data.