I finally found a fix that works. The issue is that my internet service provider (CenturyLink) router/modem DHCP name special character state had to be re-configured to allow special characters.
In your computer browser go to your modem/router configuration. The IP address, Admin user name and password is usually on a sticker on your modem/router.
Go to "Advanced Setup,"
Go to "LAN settings,"
Go to "DHCP settings,"
Go to "Option 4-set DCHP name special character state,"
Click "Allow Special Characters,"
My Hisense Roku TV immediately connected and has stayed connected. Once after a power outage, I had to repeat the process.