Hot Water not firing up boiler?

TL DR; Hot water won't come on even though no errors seem to be present in either app or wireless receiver.

Hi there,

This is a long shot as I know very little about plumbing in general but gave it a go as all the instructions were relatively straight forward, but before seeking professional advice, I wanted to ask here.

The system:
Ideal Logic 15 Boiler Downstairs
Kingspan Tank of sorts Upstairs
TPOne-M Thermostat - Controls HW and Downstairs CH
TPOne-B Thermostat - Controls Upstairs CH

I replaced the downstairs TPOne-M with the Tado Wireless Receiver and upstairs TPOne-B with the Tado Wired Thermostat - I was told to do this by Tado Support.

Im not sure if I have a Y-Plan or S-Plan or how to necessarily check but everything was wired up exactly how the app suggested and there was no question surrounding this.

Downstairs radiators are currently fitted with Tado TRVs.

Central Heating
CH works fine from what I've tested so far, I set a temperature on a particular radiator, it fires up the boiler and begins heating radiators based on valve temps, i turn the temperature low and the boiler turns off - on a basic level this is what I expected which is great.

Hot Water
HW switch is available on the app and no errors showing anywhere on either the physical Tado Wireless Receiver or app. The relay will click on the receiver when turned on and off but the boiler does not at all fire up when HW is called for.

I wondered if there was anything I was missing or how I can troubleshoot this/test this? Its going to be a PITA to have to rewire everything back to the old thermostat just to get HW so I wanted to ask for some help!

Thank you :)