On what computer operating system is your Premiere Elements 12/12.1 running? Have you updated your 12 to 12.1 using an opened project's Help Menu/Updates. If not, please do that.
For your immediate question..
You can change the "do not show again command" whenever you want. Go To Expert workspace Edit Menu/Preferences/General and place a check mark next to "Show all do not show again messages".
Please let us know if that worked for you. If not, please give more details.