Most often this happens because the missed run hasn’t been marked correctly or your app hasn’t fully synced. Hiiro needs to see which workouts you did and which you skipped before it can rebuild your plan, so make sure your recent runs are saved, the missed one is marked as skipped, and the app has an internet connection for a few minutes to update.
If it still doesn’t update, try closing and reopening the app, restarting your phone, and checking that you have a stable connection. If nothing helps, contact Hiiro support from the app and the team will look into it.