801.51(1)

(1) At or before the time the party serves his or her first motion or responsive pleading in the action.

801.51

801.51 Challenges to improper venue. Any party may challenge venue, on the grounds of noncompliance with § 801.50 or any other statute designating proper venue, by filing a motion for change of venue:

801.51(2)

(2) After the time set forth in sub. (1), upon a showing that despite reasonable diligence, the party did not discover the grounds therefor at or before that time.