writing a simple half dotted note

Hi! I want to write a half dotted note and a don"t manage. where am I wrong? Please look the attachment. Thanks!
dotted half .PNG

If it’s an isolated case, you should Force Duration, in the left sidebar, and re-enter the note. If not, you should specify the rule in Notation Options.

It looks like you might be writing in open or irregular meter, in which case you should enter the time signature by typing Shift+M for the meter popover, then enter X for an open meter. You can hide the displayed X via the Properties panel. When you use an open meter, Dorico doesn’t have any preconceived ideas about the metrical structure of each bar, so if you ask for a dotted half note, that’s what it will give you.