There are two main causes for this.
- Assigning begins on Friday for games starting a week later. Games are not announced until Sunday. If you try to enter a block during the Friday to Sunday window, it will be ineffective if the assignor has already given you a tentative assignment. You can always tell if you have a pending assignment by viewing your Arbiter calendar. If you have a pending assignment, the date on the calendar will already be colored light blue indicating a pending game (one assigned but not yet published). All blocks should be entered no later than Thursday night. If you try to enter a block and you see that the date is already colored light blue, contact the assignor immediately. Do not wait until the assignment is published as you will be charged with a turned back assignment.
- Less common is an issue where the referee is a member of more than one Arbiter group. Sometimes referees enter a block for one group, but not the group that gave you the assignment. For instance, referee A is a member of the SWISRA group and the SISL group. Referee A only enters a block for the SISL group. Referee A will still be available to receive assignments from the SWISRA group. On the Block page, always look to see that the checkboxes next to the groups you want to be affected by the block are checked.
The assignor really appreciates referees who are pro-active with their calendars.