The Fermi LAT collaboration has recently reprocessed the first 4 years of data using improved instrument calibration constants. As of today, these new data are still being validated and part of that process involves the re-analysis of known sources. While the main improvement expected from the reprocessing is in the >10 GeV angular resolution, we did find an increased number of events with the SOURCE classification, many of which survive to the CLEAN event class, in the energy range from a few hundred MeV to few GeV, the sweet spot for pulsar studies. We thus searched for pulsations from PSR B1821-24 in the globular cluster M28, the most energetic rotation-powered millisecond pulsar known. Using the new data and result of the pulsation search we reevaluate limits on the number of millisecond pulsars in M28. Portions of this research performed at NRL are sponsored by NASA DPR S-15633-Y.