Welcome to the forums. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your topics and posts, as well as connect with other members through your own private inbox!
While installing DP did you use a separate account or system account ?. Add the site server computer account to the local admin group on the DP and then install DP with default account.
In IIS, checked the permission of SYSTEM in authentication, System has not full control permission I am not sure how it has been changed. I provided System to full control as shown below and It worked for me.