Is the card still under warranty?
yes it is but its useless in my country
Have you tried reseating it?
I dont know what do you mean
Have you got the PCI-E cable plugged in?
yes I've done everything right as I think
What did you clean it with?
first I cleaned it with a Brush teeth to remove the dust but there was a sticky Dust so I removed it by a negative Screw
Have you tried it in another PC?
Yes, I have and it didn't work
Its not recommended to remove the heatsink if the card is still in warranty as it voids the warranty...
By "reseating" I mean re-installing the card in the motherboards PCI-E slot, but as you've tested it in another PC its unlikely to be the cause of the issue.
Don't use a tooth brush to clean a graphics card (or any PC component) its far to rough and could easily damage the card, also if the tooth brush had been used before it may have had some liquid/moisture on it.
I think you've killed it by ESD or damaging the PCB when cleaning.