Hive sender not switching on boiler....sometimes!

[muddipete]

Hi, so I've fitted a hive thermostat to my baxi combi boiler and all was working fine. Unfortunately the hive thermostat is no longer firing the boiler, the stat is communicating with the sender and the green light is indicating its switching on but no response from the boiler.
On further investigation I've found the boiler has an internal sender to a old wireless room stat, I'm thinking this is preventing the hive from working, but not sure why it was working previously.
Question I have is should I disconnect the internal sender completely, or should I just link the 2 black switch wires, I'm assuming this would make the boiler ON and then the hive should take control, pic of internal sender attached thanks for any advice

 

[RandomGrinch]

On further investigation I've found the boiler has an internal sender to a old wireless room stat, I'm thinking this is preventing the hive from working, but not sure why it was working previously.

If the old wireless stat was still operating and kept somewhere cold, it may still be calling for heat, allowing the Hive to operate.

Question I have is should I disconnect the internal sender completely, or should I just link the 2 black switch wires,

What is the make/model of the wireless receiver, and what boiler is it mounted into?
Ideally post a picture (although this website seems to be playing up at the mo).

 

[muddipete]

The boiler is a Baxi Duo-Tec 28, and the wireless receiver is a Salus BC600RX, I'll try and attached a pic but didn't seem to worl last time I tried, thanks

 

[muddipete]

Second try at posting image

 

[RandomGrinch]

and the wireless receiver is a Salus BC600RX,

Yes, join the two black wires together from terminals 3 COM and 4 NO, in a separate terminal block.
Safely isolate the electricity first - these wires are at mains voltage.