I don't know what you are doing wrong. Presumably you intended for
these operations to mean something different from what they actually
are because if you understood what ask is supposed to do then these
outputs are both obviously correct.
Your use of odd symbols names makes this somewhat confusing for me so
I'm just going to use x, y and z for the symbols. This is your first
query:
In [1]: print(ask(Ne(x, y), assumptions=Eq(x, z)))
None
Here you have asked if x != y based on the assumption that x == z.
Clearly the assumption gives no information to answer the query so you
get None which is the correct response because it just means
maybe/don't know in this context.
In [2]: print(ask(Eq(x, y), assumptions=Eq(x, y)))
True
Now you have asked if x == y given that x == y. Clearly the assumption
implies that the query is True and so you get True.
--
Oscar