DIAGNOSIS Yeah, this one's common. The E3 code on this unit specifically means it's detecting a low refrigerant level, which trips the pressure sensor and shuts the compressor down to protect it.
FIX For a DIY check, unplug the unit and carefully vacuum out the condenser coils on the back. If they're clogged with dust and pet hair, the system can't exchange heat properly and mimics low pressure. If cleaning doesn't clear the code, this is a sealed system issue. You'll need to call a certified HVAC technician to pressure test, find the leak, repair it, and recharge the refrigerant. Frigidaire doesn't sell refrigerant or filling ports to consumers for this.
IF THAT DIDN'T WORK The other possibility is a faulty pressure sensor itself. A tech can test this with a multimeter. If the sensor is bad, it sends a false low-pressure signal even when the charge is fine.
HEADS UP Don't ignore this or try to run the unit with the E3 code. Running a compressor with genuinely low refrigerant will burn it out completely, turning a repair into a much more expensive replacement.