I have installed one of the power managers on my Android phones, and when it reaches a v. low level of battery it offers me the option of entering “super saver” state. This turns off a number of rather useful services, most importantly the master sync service. It doesn’t turn them back on. This rather f*cks a number of data services. (NB It also turns of the wifi service which if you don’t notice will impact the bill. )
How to turn it back on.
Use the Master toggles panel! In the picture above the service is on.