try follow methods,maybe it will help.
1,reboot your network adapter of lenovo g500,
2,reinstall your network adapter of lenovo g500,
3,set static IP in WDR3500 for network adapter of lenovo g500,

moreover,do you connect via 2.4GHz or 5GHz wi-fi?
could you provide a screen shot?

Thanks for the static IP idea. Maybe it will work. I use static IP based on MAC in my Apple APE for internal routing, so that might be interesting. However the router does allow dynamic connection to other devices and the Lenovo does connect to other routers viz. APE.
Seems to still be some driver issue in the Lenovo and or firmware issue in the WDR3500. Seems, according to this site, Lenovo had a lot of issues with various routers when it upgraded to 8.1.
Right now we are going to take it to a repair centre and see what they say.
Thanks
Barry