At a customer site, they had a fujitsu monitor that was really dark but when you went to change the contrast it came up with “OSD Locked”. The official manual that I could find for google said to press buttons 3 and 4 and power it on but this didn’t work. However holding down the select/menu button and pushing the power button and keep holding the select button down until the menu appears and hey presto, one unlocked osd! Repeat the process to lock it again.