A watch that will not pair is a deflating way to end a build, and it is usually one of a handful of things.
Start with the battery. Clockstar 2.0 runs on the Li-Po battery supplied in the kit, so charge the watch fully and try the pairing again with it topped up.
Then work through the following.
Turn the phone's Bluetooth off and back on, then restart the phone.
Keep the watch and the phone within arm's reach while you pair them.
If the watch has been paired to another phone before, remove it from that phone's Bluetooth list before trying again.
If you have been coding the watch, restore the stock firmware at code.circuitmess.com. CircuitBlocks erases the watch's flash and writes a MicroPython image over the original software, so the built-in watch functions, the phone connection included, come back only once the stock firmware is back.
If you have only just finished the build, go back over the last steps of the Build Guide and check the assembly.
Clockstar 2.0 pairs over standard Bluetooth, and we do not keep a tested-handset list, so if it pairs with one phone in the house and not another, tell us both models. That comparison is the most useful thing you can send us.
If none of that helps, message us here, or email [email protected], with your order number, the phone make, model and operating system version, and what the watch shows when you try to pair. The phone model is the first thing we will ask for, so sending it up front saves a round trip.
If the watch turns out to be faulty, that is covered by the warranty and there is no 14-day or 30-day limit on it — see "Do your kits have a warranty?" for what that covers and "What do I do if my device is defective?" for what to send us. If you would simply rather not keep it, you can change your mind instead: 14 days in the EU, the EEA and the UK, and 30 days everywhere else as our own goodwill policy. "What is CircuitMess' refund policy?" has the full rules, including who pays return postage. Either way, message us here before sending anything back and we will confirm the address.