I've recently re-activated a Jetpack that had been unused for some time. I've changed the SSID, WPA key & LAN from a 192 to a 172 network (including DHCP) to make it compatible with other devices on my business network. After doing so, I'm able to connect via laptop, tablet, phone what have you to the hot spot but cant get to the Internet.
By the way, when I hard reset the device to the default settings and connect to the factory SSID, password & DHCP... everything works fine.
There is no 6210, there is the 4510L, 4620LE, 5510L, and 6620L.
Unfortunately, a Jetpack is a proprietary device that works the way Verizon wants it to work. It may and it may not work the way you might be accustom too. I cannot change the IP address or anything to do with DHCP on my Jetpack, because it will fail if I do. I can use manual assignments outside the DHCP pool with no problem. I can make the SSID anything I want with up to 32 characters.
As for the PSK, a 64 character PSK is not supported. You can use any length PSK from 8 to 63 characters and in any combination of the 96 printable ASCII characters. But, be aware there may be conflicts with certain characters that are not always translated properly between people and devices meaning one WNIC might not connect whereas all others do.
You might have one of the Jetpacks that does not allow custom subnets. Its a bummer but its a device limitation to some models. You can normally mention this requirement to VZW and they can offer to swap you out with another model that can comply with your needs.