You can try the following troubleshooting steps and even leaving it powered on with the blinking green light overnight to see if it does eventually come back. If it does not and none of the troubleshooting steps work, then it may be a hardware failure and will need to be replaced. Unfortunately, your IQ Panel 2 was on firmware 2.4.2 which would not make it compatible for a restore of your panel on an IQ Panel 4. All devices will need to be learned in manually.
Let us know if you have any additional questions thank you