File uploading error in OJS 3.1.1-4

Following are the errors we are facing while uploading files in OJS.

As author, when I try to submit article following error shows

Similarly when I try to upload website logo as an admin following error shows


I have just installed OJS for this site. No modifications in any file yet

@asmecher Your kind support will be much appreciated !

There is probably something wrong with the folder permissions both in files and public directory. PHP can not write. See How should file permissions be set? - #2 by ctgraham

@ajnyga No luck !
Is there any other solution ?

So are you sure the permissions are correct? How did you test them?