I am using Ubuntu 16.04. I have tried to download Tor Browser from the Tor website and using the Tor Browser package from the Ubuntu software application. Each time I get a message titled Signature Verification Failed. The message is: 

    You might be under attack, or there might just be a networking problem. Click Start to try the download again.  

I have tried many times, always getting the same result. I have wiped the hard drive and reloaded Ubuntu three times, and each time I got the same error. I have successfully installed Tor on my laptop which uses the same router and internet connection.