Tasks created in Marvin are synced to your calendar when all of the following conditions are met:
1. Your calendar must be setup with two-way sync. One-way sync means that events created remotely (in your google/yahoo/etc. calendar) come to Marvin.
2. If your calendar was setup with a linked category and/or label(s), the task must have the appropriate category and/or labels. If you have a category AND label(s) linked to the calendar, the task will need both the category AND all the label(s).
3. The task must be scheduled. You may have unexpected results if you use the rollover scheduled tasks or auto-schedule due tasks, so be sure to schedule the task directly if you're have issues. If you create or drag a task into your Agenda or Calendar within Marvin, you can be sure that it is scheduled (and has a time in its title).
4. The task must have a time in its title. If you create or drag a task into your Agenda or Calendar within Marvin, you can be sure that it has a time in its title (and is scheduled). Note: sometimes the time is hidden in the task's title within the Agenda or Calendar views.
5. Make sure that your Calendar is setup to sync with Marvin Tasks.
6. Make sure the Calendar isn't paused
7. Make sure the Calendar Sync strategy is enabled