I have tried all the obvious ones such as changing permission on the filesystem to 777 and removing it as root or sudo. I had one success with this method then it went back every time I eject the SD card, use it in a speaker player then try to access it again on the computer.
Tried the fsck and did work one time but I am very careful prior to removing the card by ejecting it [umount].
fsck -a /dev/sdb
Gparted didn't work. But if I've continued to try, I think one of these days it would have worked. Rebooted so many times that I felt like I was using Windows Vista.
The dd command didn't seem to work at all
dd if=/dev/zero of=/dev/sdb bs=1M count=10
I have noticed one time where my SD card had residual trash on the card .Trash-1000; however, nothing can remove it to include root. Then found out that you have to delete the user's Trash then umount and remount. This worked once then failed again.
rm -rf ~/.local/share/Trash/*
A different scenario happened to where I plug in then eject then insert again then eventually it worked. From Nemo file manager is whether or not I had the delete option which indicated that the SD card is now in read-write mode.
I have tried umounting then remount with rw options:
sudo fdisk -lor
sudo mount -t vfat -o rw /dev/sdb1 /mnt
sudo mount -o remount,rw /dev/sdb1 /media/username/usbname
Finally I really think that by adding myself and the root into the disk group worked.
sudo usermod -G disk --append username
sudo usermod -G disk --append root
