SharePoint 401 Unauthorized Repeated on login popup - DisableLoopbackCheck

Question

I have set up my new SharePoint 2019 environment and created a site collection and web application. But as soon as I join in, a popup appears asking for my credentials and it keeps asking, as shown in the following image:

 

• I'm sure I entered the right credentials.
• Trying to login by the Farm Account, and site collection administrator. 

Answer 1

You can Solve this issue by adding the DisableLoopbackCheck in the registry.

How to Add DisableLoopbackCheck in the registry?

1. Click Start, click Run, type regedit or press (windows + R) write
   regedit, then click OK.
2. In Registry Editor go to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
3. Right-click Lsa, point to New, and then click DWORD (32-bit) Value.
4. Name the key DisableLoopbackCheck
5. Double click DisableLoopbackCheck Key, in Value date: box type 1.
6. Click OK, and close Registry Editor
7. Restart IIS in the CMD, by write iisreset command.