Is the target board powered on? Note that the MiniProg3 (i.e. USB) is not recommended as a power source for your target boards.
Are the USB drivers installed? You should see the MiniProg3 under Universal Serial Bus controllers in the Device Manager. Open the properties and check that the device is working properly.
Does your selected device and silicon version match? PSoC creator supports preproduction devices but you need to be sure that your project is built for the silicon version you have on the target. Use the Device Selector to check that your project and silicon match. You select the revision from the bottom right-hand corner of the selector.
When silicon and project are mismatched the device cannot be acquired. To force the tool to try the acquisition, and generate useful error messages, open the “Select Debug Target” dialog from the Debug menu.
Double-click on the PSoC device. If there is a mismatch you will get an error of the form: dbg.M0033: The selected debug target ’PSoC3 CY8C3866AXI-040 ES2’ is not compatible with the project’s selected device ’CY8C3866AXI-040 ES1’.