Sitefinity Quantum application, add-ons, WebAgency ,This add

when testing Sitefinity Quantum application :

open dashboard,go to localhost:60876/.../add-ons

open  WebAgency  , status " Inactive"

when try to activation an error appera :

(This add-on has not been activated successfully. Please check the log for further information )

if i try again ,  a new error 

(

WebAgency
This add-on cannot be activated, because its files are missing or corrupted

)

how to fix this issue ?