When does Attach Top/Base not work?

[d.whynot]

I'm perplexed at times when the Attach Top/Base feature doesn't work. In my example video I have a steel beam and I wish to attach the steel column below to it and it won't attach. I've tried creating reference planes and levels to target the attachement, but the column just won't select for attachement. I've had this happen on a few occasions. My question is, why and under what conditions will attacting a column to a beam not work, so I can prevent this from happening in the future?

[clintonc]

I'm perplexed at times when the Attach Top/Base feature doesn't work. In my example video I have a steel beam and I wish to attach the steel column below to it and it won't attach. I've tried creating reference planes and levels to target the attachement, but the column just won't select for attachement. I've had this happen on a few occasions. My question is, why and under what conditions will attacting a column to a beam not work, so I can prevent this from happening in the future?

have you tried setting the top offset to 0?

[d.whynot]

Yes, I did try setting the top to zero, but still not luck