Yeah, normally those blockages come from the caster’s belief system.
To give you one example:
Gabriel had huge issues contacting me for quite a while.
That was caused by a failure from the Angelic pantheon,
on a request of mine.
I had lost trust,
and simply didn’t want them around.
Still,
Gabriel did manage to reach me,
by going through a medium,
which seeked out my contanct on his behalf.
My personal shields and defense didn’t allow him,
to reach me directly,
yet,
he did manage to reach me.
But it took longer, and more effort then necessary.
Most of the time,
we’re not aware of our own mental blockages,
and shieldings being associated with them.
But you can,
consciously decide to call a specific angel or demon,
and intentionally open your shields up for it.
Normally not.
And in most cases,
they would at least take the time,
to tell you specifically,
what being is a problem for them,
so you could adjust and for example,
send Azazel away, in order to speak to Gabriel.
There are some specifically not liking each other that much,
just like in a big family,
some fractions don’t like each other.
But,
normally they won’t ignore a request because of it,
and simply tell you: “it’s okay, i come, i help you. but please send x away, for the time working with me.”
Sincerely,
¥’Berioth