Co-incident with adding a larger SD card (but may not be connected) on opening Navigator it says "The Navigator folder is set as read-only. This could be because the device has been updated to Android 4.4 or higher".
Yes, it has, it is on Android version 5.0. But it doesn't tell me what to do about it. What can I do, anyone, please? Surely there is a way round this.
If you are on a rooted phone it's quite easy. Look for an app like SDFix or similar.
Otherwise search this forum for "read only" to find explanations and workarounds. But be warned, those fixes won't be working for Marshmallow anymore, at least to my current knowledge, so better adjust your directory structure to what Android requires fron 4.4 onwards.