Cannot connect to wireless network

I work for a company where I support wireless networking. I had a customer who was trying to connect via wireless and so he selected out network but when he tried to connect then he got some message that "Windows cannot connect to" and our network name. So, I managed to go to the wireless networks and add a profile for our network, but still he got the same message. Even after turning the Windows Firewall off nothing worked although he was getting good signal level. Is there any fix for this problem?

Did you try to uninstall the wireless adapter on his computer/laptop and then tried to reinstall it again and check if that could work?

When you have removed and reinstalled the wireless adapter, then try to delete every available network on the wireless network manager and then try to reconfigure wireless network. Incase this is not working for him then try to check msconfig and make sure that it is running normally at the startup.