one monitor it might have been easy to locate a user manual that might offer trouble shooting assistance. Unfortunately this is not the case and you left us no mention of monitor model number nor type of connection to the PC (VGA or DVI).
Providing the COMPLETE message or messages would work wonders too.
Try unlocking the OSD - some monitors do this by pressing button 1 plus the upward pointing triangle button for a minimum of ten seconds. The power lock is sometimes enabled and disabled by pressing button 1 and the downward pointing triangle button for a minimum of ten seconds.
If you have it READ the fine manual the monitor came with for guidance.
Envision monitor about 3 years old, won't let me turn screen off at controls in the front and brighteness control sign keeps popping up, which I have to use "1" button to try and get rid of...it says unlocking power button. Help! Won't stop and I'm getting tired of not knowing what to do! thanks.