Some assignment settings become unavailable once participants have received the activity. Knowly locks them so people already working aren't moved onto changed rules halfway through.
What locks once the assignment has been sent
The lock kicks in the first time the assignment is sent to participants. From then on, the settings that decide how the assignment works can't be changed:
the Submission type — whether participants Write a text or Check a box,
for a manager assignment, whether it's Per employee or a Single submission,
Require managers to approve participants' submissions, and the level of manager engagement that goes with it (Only approval or Approve and comment when approval is on; Read submissions or Read and comment on submissions when it's off),
the Audience — participants or managers.
Knowly explains this right where you'd change them: "These options can only be changed before sending the assignment for the first time. To change the options, you'll need to duplicate this assignment and select other options in the new assignment."
What you can still change
The content stays editable. You can update the assignment's name, its description, and the instruction text a manager sees at any time — none of those change the rules a participant is working under.
If you need to change a locked setting
Duplicate the assignment, pick the settings you want in the copy, and use the copy in your journey. The original keeps its history, and the participants already working in it stay on the rules they started with.