Hi, I tested my plugin in 5.5 and it seems to save all settings correctly to DefaultEngine.ini. Maybe you can compare and find out what is different in your plugin.
It’s open source so you can download if you prefer, this is the file with the settings: unreal-engine/Source/PubnubLibrary/Public/Config/PubnubSettings.h at master · pubnub/unreal-engine · GitHub