I can't not change the site language into Vietnamese

Envato Authors ThemeForest
#1

Screen Shot 2022-03-14 at 20.50.43
Screen Shot 2022-03-14 at 20.50.432160×1352 96.2 KB

I can not change the site language into Vietnamese. Then i can not make any change because of this fault.
How I can fix this mistake?
Thank you

#2

Hi,

Contact with your purchase item author hope they will helped!

Thanks!