Still having this problem. No matter what IP range I use, issue is the same. Static IPs work fine, but the MIFI will not issue more than one IP address.
If you are still under warranty then I suggest contacting VZW to have them replace the device.
It will be easy for a phone or store rep to work though the steps and identify the defect since it is so easily re-creatable.
DHCP is a feature that should work on the 4620L. I have access to many of these devices all of which operate as you would normally expect them to. Perhaps your current jetpack pulled a bad firmware update somewhere in the past. The only thing you as a user can do is try to re-flash or update the firmware to the latest version that is available on VZWs site.