T-cell-15 generating only in service mode

[capritex]

Hayward T-cell-15, controller is aqua rite, controller inside the house is jandylink rs
I'm seeing a strange problem and appreciate any tips.

In service mode, the following happens to the leds in aqua rite set to Auto mode:
- for first 30 seconds of pump turning on: power led on, "aqualink rs" led flashing, "no flow" led flashing
- after 30 seconds, "no flow" turns off, "generating" turns on
- turning aqua rite off, causes "generating" to turn off.

So far, so good.

In auto mode though...
- power led on, "aqualink rs" led on, and for just 2-3 seconds "no flow" flashes furiously and then turns off
- after this, nothing changes and "generating" led never turns on, an no chlorine is generated.

Could someone tell me why/how does aqua rite care about service mode?
Thanks in advance!!