SSRS Reporting Issues--can't change credentials and reports asking for more information to run than before

Hello,

A issue we have encountered is that in report builder I can successfully add and connect to a datasource, but I can't add a dataset from it, it says incorrect login. I did notice that the credentials settings in the datasource do not match what they should be everywhere else and am thinking this could be part of the issue, but that screen is greyed out and I am unable to make an update, even if I run it as an administrator.

We have gone through all of the areas where permissions are set, and I should have full access but seem to still be hitting some road blocks.