This may help.
I can't save pictures or videos to my media card
Try one of the following:
Delete old media files to free up storage space and try again.
Insert a different media card.
In the File Manager app, browse to your media card. Make sure that the Camera folder exists and is available. If necessary, create a new folder called Camera.
In the File Manager app, browse to your media card. Check if there are any other files called Camera. Delete or move any other files called Camera to a different folder.
The full help file link