User being prompted for Credential when download an excel file

I have a user who goes to a public HTTPS site to download an excel file and she is being prompted for Windows Security credential. She types in her username and password and hits okay, but it prompts for it again and does it for total of three times before letting her open the file.

For now I found two alternatives,

1. I entered her username and password in Windows credential manager and it is autofilled when it prompts so she has to just click okay three times before she is able to access the file.

2. All she has to do is hit "Cancel" once and it will still give her the option to Save or Open the file.

So I am curious as to why it is prompting her for credential and I had her use another box which worked correctly without any credential prompts.

This is not a Sharepoint site. It doesn't seem to prompt for login if its none office files.

Thank you for your time and any response.

I have ran a repair on Office suite and its still the same.

Also, I tried what is listed here:

Prompt for Credentials When Accessing FQDN Sites From a Windows Vista or Windows 7 Computer

and restarted PC but it is still doing the samething.