Hello Callum -
I responded to your support case, but wanted to answer on here as well, as it may prove useful to someone else in the future.
From the behavior you reported, I assume the Static Password was programmed over Yubico OTP, and now the Personalization Tool will report either "Slot 1 configured" or "Slot 2 configured." If this is the case, you probably overwrote the default Yubico OTP programming that was in Configuration Slot 1 by default. If this is the case, you shouldn't run into any issues unless you use Yubico OTP to log into Salesforce (it's the only service I'm aware of that DOESN'T allow user-programmed Yubico OTP). You'll just need to reprogram Yubico OTP using the Personalization Tool.
The instructions for programming Yubico OTP can be found here -
https://www.yubico.com/products/service ... ey-upload/The PDF file linked on that webpage walks you through the entire process. Make sure you complete through the "Upload to Yubico" portion of the instructions, as this is required for the Yubico OTP to authenticate to the YubiCloud. From your report, I'd guess Slot 1 contains Static Password and Slot 2 is blank (or vise versa). You'll want to program Yubico OTP into the empty slot, and then you have the option to swap Configuration Slots if necessary to return to your earlier setup. Swapping Configuration Slots is done through the Personalization Tool (Settings > Update Settings, select one of the Configuration Slots, and click "Swap").
If you happen to swap Configuration Slots when only one Slot is programmed, it will work, but as there is only one Slot configured, short press (~ 1 second) is the only option. Attempting to long press (~ 3-4 seconds) will result in the only programmed Slot's output being send after about ~ 1 second.
Hope this helps!
Best Regards,
Chris
Yubico Support