If you cannot connect your Salesforce account, first check to ensure that API access is enabled. If this is enabled and you are still having troubles, the next place to check is Session Settings.
If these settings are as below, the connection will fail due to the fact that Geckoboard authenticates and then queries using a different set of IP addresses.
Instead, set Session Settings to (only) Lock sessions to the domain in which they were first used. This will allow us to connect to your Salesforce reports. This should get you going!
If you're still having trouble connecting to your Salesforce account, get in touch.