Gmod wont work,don't know why

*first of all,sorry if i have any grammer mistake,my english isn’t perfect yet.

after long time that i did not play Gmod , i wanted to play again to see what change.
when i enter the game i have an error that say:

Engine Error
Could not load libery client

i tried to remove the game and install once again but its didn’t work.

Thanks for your support.