If the oven display is showing LOC, then the lockout feature was enabled. Press and hold the key pad with the padlock symbol for 3+ seconds. This is just below the Timer On/Off key pad and to the right of the Light key pad. You should see the word DOOR and the padlock icon flash until the door is unlocked and the control panel is released.
If the word DOOR and the padlock icon are lit, then the oven is in the self-clean mode. The lock should release after you cancel the self-cleaning cycle by pressing off and the oven cools down (at least one hour). Unfortunately, sometimes the heat of the self-clean cycle will damage the oven. Either the oven temperature sensor will not give the release signal or the door lock will not disengage. In that case, the oven needs to have the correct part serviced.
The documentation for the Frigidaire FGGS3065PF is available on the product page at Home Depot: https://www.homedepot.com/p/Frigidaire-Gallery-30-in-4-5-cu-ft-Slide-In-Gas-Range-with-Self-Cleaning-Convection-Oven-in-Stainless-FGGS3065PF/204759413
. See page 15 for the Oven Lockout feature. See page 28 for the self-cleaning information.
I hope this helps.