I asked this on STW, but figure some on here prolly don't frequent there, so I thought I'd ask here too.

I’ve been slowly installing all the bits for the GRX groupset to the RAG+. Last thing I need to do is get the 1x setup and running, I’ve followed the instructions for the ST-RX810-R dual control lever and was following the instructions for the RD-RX812 rear derailleur.

When attempting to shift up out of the smallest rear cog, nothing happens. I only get one click on the level, I can’t get the multi-click jump to work at all. Even putting the inner cable under more tension, it doesn’t feel like it’s being pulled at all. I’ve never had dual control levers before, so have no idea about how to diagnose and fix what’s going on.

Can someone point me to a youtube video or something showing how to get this stuff working? Do I need a cable tensioner doofa? Should I just take it to someone who has a clue?

I've not played with these but from the sounds of it, it does sound like a cable tension issue.

Does it change gear at all? Was it clicked all the way through to the smallest cog to start with when you fitted the cable?

I once had a 'friend' who could only get 9 gears on a 10 speed as the shifter was already in the the second gear when fitted

what they say

So
1. pull cable with hand and click through gears unattached to rear mech and you should feel the cable move - it does not move then a lever /routing issue

2. Set lever so its at lowest "puling gently" the cable out as you click

3. Attach cable loosely to mech with say a loop - click lever and you should see the cable pulling WITHOUT TENSION- its slack so no mech movement - if not lever again

4.Pull on loops yourself by hand just to check the mech can travel through all gear choices - if it wont adjust mech till it does or its a mech issue

5.Attach cable to mech and click if it wont move then back to a gear lever issue or routing issue as it cannot apply enough force to move the mech - had that once with a weird front mech set up - Gd that was a pain to sort
best of luck
Generic instructions rather than for your set up

Took all the cables off, put them all back on, following the instructions. It works. No idea what was going on last night. Now going to ride up and down the High Street and grin like a loon.