Made by SLoanLED
This is a grey 6 1/2cm by 7 1/2cm box that says LiquaLED in its moulding, on the label it says SloanLED 40 Control, and its a 12v system.
SloanLED control 40 can manage up to 40 LED's and is designed for end users to easily repair there lighting system or other people to build in new lights to there hot tubs.
It consists of a 2 pin amp connector on a 2 core cable (Black and white twisted), which goes to a grey box which manages the power to 2 male 4 pin connectors designed to daisy chain LED lighting in a spa / hot tub.
Please see images for spec on grey box.
How to test
Symptom - No LED's lighting on your hot tub.
With a multimeter test to see if the system is getting power, and if so test with multimeter on the pins inside the male connectors, you should get 12v on 1 of the pins on both of the male connectors. And if not you will need a new control unit.
If you have a 12v coming from the connectors then you may have a faulty LED or complete faulty chain of LED's, testing is much the same as old Christmas tree lights from there on.