When you want to guess about other people's emotions or intentions in the past, you say that they "seemed to" do something:

Everyone seemed to have a good time at Ella's party, wouldn't you say?

You seemed to be confused earlier when I was giving the instructions. Do you have any questions?

Will seemed to like the gift you gave him.

Tne negative version of "seemed to" can be either "didn't seem to ___" or "seemed not to ___":

They didn't seem to hear what I said.

They seemed not to hear what I said.

"Seemed not to ___" is a little more formal.