You didn't say which DAW you're using it with. If it's anything other than Studio One, you'll probably need to make sure it's back in the correct mode after the firmware update.
From the Quick Start Guide:
The FaderPort offers customized operation modes for five (5) major DAWs. To select your Operation Mode, press and hold the NEXT button while powering on your FaderPort, then press the button for the desired mode (see below)
Studio One - Solo
MCU (Logic) - Mute
MCU (Live) - Arm
MCU (Cubase) - Bypass
HUI (ProTools) - Touch
If that doesn't solve the problem, I'd recommend running the firmware update again to see if that solves the problem, as I've cleared similar issues with a second attempt at updating the firmware. Select 'Update Anyway' when the dialog box prompts that the FaderPort 2018 firmware is up-to-date.