Failed to save '.env' file: Unable to write file

I'm trying to save changes to a file in VSCode but suddenly getting this error-

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The project folder is located in Local Disk partition on my hard disk, and it is mounted on startup as can be seen-

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How can I resolve this issue?

Edit 1:- Here's the list of commands that @heynnema asked to run-

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I also tried the command sudo fsck -f /dev/sda4 after booting from live usb, but it didn't fix the issue.

Solution 1:

Your local disk/partition has a file system problem, and has become read-only.

boot to a Ubuntu Live DVD/USB in “Try Ubuntu” mode
open a terminal window by pressing Ctrl+Alt+T
type sudo fdisk -l
identify the /dev/sdXX device name for your "Linux Filesystem"
type sudo fsck -f /dev/sdXX, replacing sdXX with the number you found earlier
repeat the fsck command if there were errors
type reboot