Yup it seems to have been a distance thing. When I moved the CAP birds closer, I could get them vectored.
I assume same for SEAD, but I haven't tried it yet.
Not sure what the magic number is, but the first time they were about 100 nm away. I called them when about 70 miles from the target area (closer to them) so I thought there might be enough time...next time they were more like 30 nm away...but behind me... LOL they didn't catch up in time anyway...