Welcome to TPG Community!
What is the OS of your Desktop computer? Is it running on Windows 10? Do you have any other device connected to your modem? (Ex. Mobile phone, tablet, laptop) And are they working?
I have searched some similar issues on Whirlpool and found out that it's a common issue on Win 10 OS. Check this link for your reference.
You can also try to manually assign an IP address to your Desktop and check if it's going to work.