执行Imperosnation后无法访问UNC共享

We have to access a network UNC share which is say allowing access to USER1. Our exe is running with LOCAL SYSTEM account. In the exe, we do Impersonation with "USER1" credentials so that exe can access UNC share. But after doing the impersonation, we are still getting error "Access denied" while accessing that UNC share.We have to access a network UNC share which is