But I checked them all with my multimeter and it says I have good connectivity.
Bad or marginal connections often appear good when you test them this way. The pressure of the probe tends to compress the joint together and make it more conductive. But as soon as you remove the probe, it will go back to being a bad or marginal connection.
I don't want to solder it until I know it works. Otherwise I won't be able to return it.
If we determine that a product has been properly connected and programmed and still does not work, we will be happy to replace it within our 30 day warranty period. For many products, proper connections require soldering.
If we see that the device has not been properly connected or has soldering problems, we will request that you correct those problems and re-test the device.
The overwhelming majority of problems we see go away once the device is properly connected.