Gscn showing error white uploading zip file

I am getting the following error in gscan.ghost.org

Uh-Oh, There was an error.

Please select a valid zip file.

Please select a valid zip file.
UnsupportedMediaTypeError: Please select a valid zip file. at new UnsupportedMediaTypeError (/opt/gscan/shared/node_modules/ghost-ignition/lib/errors/index.js:128:23) at uploadValidation (/opt/gscan/releases/2019-05-14T19:12:32.593Z/app/middlewares/upload-validation.js:37:21) at Layer.handle [as handle_request] (/opt/gscan/shared/node_modules/express/lib/router/layer.js:95:5) at next (/opt/gscan/shared/node_modules/express/lib/router/route.js:137:13) at Immediate._onImmediate (/opt/gscan/shared/node_modules/multer/lib/make-middleware.js:53:37) at runCallback (timers.js:706:11) at tryOnImmediate (timers.js:676:5) at processImmediate (timers.js:658:5)

I uploaded casper theme zip file too and getting same error.