The service would have offered checking and savings accounts with various financial institutions (including Citigroup) inside the Google Pay environment to U.S.-based consumers.
But perhaps the rapid acceleration of digital banking (in part due to the COVID-19 pandemic) made Plex a weaker product/market fit than initially thought. Both incumbents and neobanks have ramped up efforts to meet such strong demand. One thing is for sure: digital / mobile banking is a more crowded market than two years ago when the Plex blueprint was initially conceived.
Did Google get cold feet? It sure seems like it. However, I wouldn’t be surprised if Plex get resurrected (albeit in a new form), especially if market conditions improve in the near future.