Testing credentials

Hi

Since migrating from 2012 R2 to 2014 i receive a daily email telling me that the credentials on some jobs has not been tested.

So i go in a test. 99% of the time i get success. However i have noticed that a number of areas that the account selection is greyed out, in particular SQL and Shadow copy.

This is where some of my jobs appear to fail, on the SQL credentials, but i am unable to change them to test another account.

How cant i get this ungreyed and change the SQL account for test.

thanks

Olly