System is Arch Linux. NTFS-3G is installed. I have had this problem on Gnome (Nautilus) and KDE (Dolphin). I already tried fixing it with Testdisk. No success. Any help is appreciated.
UPDATE: I have re-formatted the disk and it is working now. Thank you for all your suggestions and tips.
Disks mounted via your user are mounted differently than when you sudo or with root. The driver needs FUSE support to allow you to mount it via your user.
You can find more info here: https://wiki.archlinux.org/title/NTFS-3G#Allowing_user_to_mount
I ran Nautilus with root privileges, same error message. I will read about FUSE support, though, thanks.