You probably have one or more IP addresses set manually. The easy way to sort it would be to change all devices connecting to the router to have IP addresses assigned automatically and also to check that your router is set to use DHCP to assign IP addresses. If, for sme reason you do not wish to use DHCP to automatically allocate addresses then you need to examine the DHCP table in your router, identify what IP addresses are assigned to what devices and ensure that none of your manual settings is conflicting with any other.
Thank you. However, I should have told you that I'm using a Verizon MiFi which receives an Internet signal - then transmits it to about a 30' radius. There are no settings in the MiFi. I've tried ipconfig /release, then ipconfig /renew (with each machine shut down while I'm adjusting the IP with the other. However, I'm getting a message on ipconfig /renew that says I can't do that until I disconnect the media (something). Next time I try this, I'll write down the actual message I'm getting and relay it on the thread. Thanks again.