i got problem that my flash drive couldnt be accessed and visible on my computer..
but its have been installed when i plug in to my computer..
why its happened?

its pop-up that drive ' no media ' and its appeared as ' Generic USB Mass Storage ' on Ubuntu

would anybody help this noob..thanks

What do you want from it?
If just want to repair it , use specific utils, it depend on which controller its based on.
If controller Toshiba (often for Kingston) , try: 3S_USB6690_OnCardSorting_V4.024 or SSS_6686_TC58NC6686_MPTOOL_v2150 , but forget about your data.

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Angel Data Recovery

thanks for feedback..
so i cant get back my data?

Yes, you can't.
Good engineer in DataRecovery service - could.
Need proper tools, soldering skill ( to solder out all chips) specific knowledge.
Find someone near you

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Angel Data Recovery

It is possible. You need:

solder station for SMD components
Flash memory reader
Software to put the data back

Here it is described in details:
Practical USB Flash Disk Data Recovery

But it is not for everyone - better find a nearest data recovery service.