This only applies to users that have already upgraded their lightgun to 1.1.0 or 1.1.1 firmware. If your lightgun is still on 1.0.16.3, then you can safely upgrade to the latest 1.1.2 release.
We recently found a regression in the 1.1.0 firmware. The regression was with storage for the Player Id in the flash memory where it was zeroed unintentionally. Having an incorrect Player Id could prevent ARC from loading settings correctly.
If you have already upgraded your lightgun to 1.1.0 or 1.1.1 versions, you can do a factory reset using the on-board menu system. This will re-initialize the flash memory, setting the correct Player Id. Using the menu system is documented here: https://blamcon.com/get-started-with-blamcon/in-gun-menu-system/#Factory_Reset
If you have already upgraded your lightgun to 1.1.0 or 1.1.1 versions then you can manually upgrade to 1.1.2, regardless of whether a factory reset was performed or not. It will detect the condition and correct it by setting the Player Id to Player 1, the default setting.
The fix has been applied to 1.1.2 which is now available on https://blamcon.com/support/firmware/. Manual upgrading instructions are on the firmware download page.