What would be causing twitter "replys" to not show up on the intended receivers page?

[James Smith]

Do you have to be followed by the person before you can do a reply that shows up on their page? I did a reply on a page and it showed on my page but not on theirs. A friend checked as well in case it was just my perspective as the tweeter, but they saw nothing as well. Please help ??
I did wonder if the other person may have a setting on that is doing that - like maybe they only read incoming from those they follow - is that possible ?

[Rod Knee]

You may be blocked ?

This can be done individually or as a default that would cover all those followers not being followed in turn, as I understand it, but don't quote me on that.

If you haven't done anything to deserve being blocked I would think it is the setting default they are using at the moment.