File privileges problem on USB thumbdrive

[Bret Busby]

Hello.

This applies equally to UbuntuMATE 20.04.x and 16.04.x .

I have a USB thumbdrive, which is formatted as FAT32.

I want to move the files written to it, to another medium, so as to
reuse the thumbdrive for writing.

I have previously done this, with this thumbdrive, and, with other
thumbdrives of the same model, capacity (128GB), and manufacturer.

However, now, whilst file managers (caja and PCmanFM) show me, as the
owner of the files, with Read and write folder access, no file access
privilege is shown in the caja file manager, and, I can not use cut
(and thence paste to another destination) or rename functionality on
the files, and, trying to use chmod 777 and sudo chmod 777 , both
return the error "file system is read only".

ls  -l shows
-rw -r--r--
for the files.

As I am supposed to be able, as the shown owner of the files, both
read and write to, the files, why does the operating system designate
them as read-only, and, how do I overcome this?

-- 
Bret Busby
Armadale
West Australia
..............