Why is there no "Last" price for Forex pairs?
The Last column does not show the most recent trade for currency pairs but either the midpoint of the most recent bid/ask price or if not available then the previous day closing price. This is not a market data error but rather the nature of the Forex market.
The global Forex market is what is referred to as an "OTC" (Over the Counter) market. Unlike the options, futures or listed equity markets, there is no central reporting facility for OTC markets, including Forex. Hence there is no official "tape". The Last Traded Price for Forex depends entirely upon where you look. Bloomberg, Reuters, Yahoo, Google, IB, etc will all have different combinations of pools of liquidity from which they are gleaning this information. Since there is no official "Last Price" for Forex, IB cannot report one on our TWS. The previous day's closing price is the last traded price from the liquidity providers IB does business with. It may not match the last traded price for the previous day from other agencies who might have access to additional--or less--liquidity providers than does IB.