Can't update data source credentials

Thank you for the response but even on the admin (which controlled gateway) it would say this same thing but no credentials required)-screenshot below. 

I did however by trial and error got everything working.
For someone else, 

1. Updated gateway (this needed to be done so didn't resolve issue right away but maybe helped eventually)

2. Added gateway to azure (used the gateway admin account)

3. selected to Skip test connection in gateway config within Power BI (got rid of unknown error or impersonation error on gateway)-after step 2&3- gateway went online

4. This is weird as we've never had to do this but I couldn't see the credentials in there before but I changed credentials on the sql server datasource using that gateway from the admin credentials to my current windows creds & password (this seems like it could be a problem when our passwords change but I'll make note.)

NOTE:
It seems like Power BI needs to update their troubleshooting guides and more information to help in resolving error messages. There was no one place to check everything, I found help through here mostly reading tons and tons of Q&A of what other people did just clicking around themselves.  They also really work to prevent people opening support tickets. Thank goodness for the community sharing their own experiences.