The behavior that you are describing does not sound normal. Restoring the defaults on the router might be what is needed here. If you could provide us with the specific model number for your router we could try to send you the steps.
Otherwise the generic steps are to find the pin hole sized reset button, insert a paper clip, press it down for 15 seconds (while powered on) and allow the router to reboot. The next time you attempt to access the router configuration page you should be able to enter the admin password correctly. If not then your router is defective and will need to be replaced under the warranty.
VZW tech support is a good place to go for a problem like this. They can walk you though the reset as well as order the replacement device if necessary. Post back your results and let us know if you need any other help.