Network Extender intermittently working

The network extender I currently have installed on my network intermittently works. Most times that it does not work in normal operation it keeps a quick flashing red SYS light that after reading the service manual for the device would normally indicate "Security Gateway contacted successfully, VPN setup in progress" however it does not always go through the normal boot where the quick flashing would go to the slow flashing red then return back to a normal operating solid LED.

I have taken the following steps for troubleshooting the issue;

1. Restart the modem and router.

2. Unplug the Network extender, allow 30 minutes to pass and power on the network extender and allowed 24 hours to gain a GPS signal and return to normal operation.

3. Opened the following ports on the router to the IP address of the network extender: 500, 4500, 53, 52428.

4. Restarted all 4 Verizon Wireless cellular phones that would be attached to and use the network extender for service.

Thank you for any support.