Loan interest rate lock

[Ben Duq]

I was quoted an interest rate on a good faith estimate and the loan was sent to under writing/ loan approval two weeks ago. Just today my loan officer emailed me and is quoting me a rate about 1.25% higher. Can anyone explain how this could have happened. I thought the rate gets locked in at the point of signing the good faith estimate with the loan rate quoted on the day of preparation. Did my loan officer drop the ball and not lock me in? Or do I have to wait for the loan to come out of underwriting to get a final interest rate?