Wired Ring doorbell with Friedland

Hi, I’m looking for some help with my wired Ring door bell. I have the friedland type 6 chime which runs on 8-16v so thought it would be enough to meet the ring requirements, however once a put a jumper cable between T3 and F2 the doorbell flashes, meaning I don’t have enough power?? I’ve attached images of the transformer also which is next to the master electrical box. What would be the best way of getting it to work?