Windows Offline Files Not Available

For a while a number of people here have been using the Offline Files option in windows from laptops. Recently the option has ‘disappeared’ from a variety of mapped network drives, ie they cannot make any files in certain locations available, the option isn’t on the drop down menu. Some mapped drives still retain this option, but re-mapping a drive which does not have the option, still does not restore it. Does anyone know why it happens and also how to re-instate the option for all drives?