Referees are limited to requesting games that are within their "Game Strength" rating. The Game Strength rating is a measure of their ability to referee games of varying difficulty. If a referee see's a "lock" icon on a game position in their game list, there may be several reasons they can't request the game, one of which is that their Game Strength rating is not high enough.
If your organization is assigning referee Game Strength ratings to referees manually (rather than having the system calculate their rating), you can change their rating on their profile page.
Step 1: Go to the Referee Management module's list of referees.
Step 2: Use the search and filters to find the referee you want. Then click on their name to go to their profile.
Step 3: Click on the Administration tab.
Step 4: Click the Edit button
Step 5: In the Game Strength setting, click the Change button.
Step 6: Select the Game Rating that you want to assign to the referee, and click OK.
Step 6: Click Save