I would always hit certain notes when using scales that were technically correct but did not work. I wondered if I was playing it against the wrong portion of a chord progression, or it was only to be used for major or minor, etc. I went looking today and found this helpful explanation, which...
Check out the suggestions for modal scale changes over the chords (hit the "Show More" button) and apply them to this very relaxing blues. It is a nice practice tool.
In A
In G