Three possible reasons:
If you edit cargroup CHEAT1, you need to enter cheat EVERYONEISPOOR to notice any change.
When editing, take a look if files are read-only. If yes, then right-click file, go to properties and set read-only off.
If editing cargroups, remember that maximum number of defined vehicles in one group is 23.
And, I would recommend using manual method of modding, instead of SAUE use regular Notepad. Most reliable tool so far.