I'm trying to buy using OmniCoin, but the "Buy" button doesn't work. What can I do?

Open the config.json file in the C:\Users\[your_user]\AppData\Roaming\OmniBazaar directory.

Make sure there is no user name or password in the rpc_user and rpc_password fields. Those fields should look like this:

"rpc_user": "",
"rpc_password": "",