SL V1 and AL V1 controllers cannot be detected/controlled.
  1. In device manager, if the controller shows up as “LIAN LI’’, then the firmware needs to be updated. Go to https://lian-li.com/l-connect3/L3_update_manually/ to download local update tool. 
  2. If the controller shows the proper product name, then completely power off and reboot the system. 
After Boot, Fans Revert to Rainbow and L-Connect 3 Loses Lighting & Speed Control – Requires Reboot

1.  First, confirm that L-Connect 3 is on the latest version.

2. Go to Settings > General and input “7s” in the blank box to delay service startup.
➡ If the issue persists, try 12s.
➡ If still unresolved, initiate RMA for the controller or pump block.

Selected PWM mode on L-Connect, but fan speed doesn't sync to motherboard.

Please enter your MB BIOS and select the connected fan header to PWM mode (not DC mode nor Auto mode).

I don't have enough RGB port and I don’t want my fans sync to MB, do I need to connect the 5V ARGB cable?

If you are not connecting 5V ARGB cable from the controller, you can only control the RGB from L-Connect.

How to check if UNI FAN is connected to PC or not?

– Check your [Computer Management] → [Device Manager] – If your MB detected UNI FAN, it would show [LIAN LI] under [Universal Serial Bus Device] – If there are error under [Universal Serial Bus Controllers], please contact your MB company for help. -Check if all 3 cables of the controller are correctly connected to the MB. Switch another USB2.0 header if necessary.

Which fan header shall I connect to?

Recommend you connect the controller’s PWM cable to the system/chassis fan header (not the CPU nor pump fan header).

You could wire the fan’s PWM cable to the CPU header directly if you use UNI FANs for your AIO.