I'm positive that you want to be able to connect with your employees at all times! Let's try some troubleshooting with this modem and figure everything out for you.
Each time you connect a PC with a modem, a new IP address is assigned. If the error you described occurs, this means that the IP address did not recycle properly(which is why they get the error that it's already in use). My best recommendation is to turn off the PC, remove the modem, and do a complete shutdown, restart of the PC. Once completed, try again and they should have no problem! Please let me know if you need any additional assistance. Thanks and enjoy your day!
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