Everytime I invite someone for RBGs, they auto-decline it. I've even had them just add my battle tag and invite them, but it still declines.

make sure you have 1.8.0 installed.  also, there are some addons (elvui) that will auto-accept group invites.  you will want to disable that option

I do have 1.8.0 and disabled all other addons. Only about 1 out of 20 people it accepts the invite. I'm not the only one with this problem. It was working last night before the server merge.

Hi Myoku.

Can you please try this? Are you able to accept friend / group invites with oQueue disabled?

If you are not able to accept friend / group invites when you have oQueue disabled, then there is a glitch with the realm merge. 

I am on a non-merged ream, and Oqueue randomly dumps me from groups that I join instantly, or dumps others that I invite to groups that I from. It happens in less than a second, so couldnt be a human doing it.

I am using Elvui, I have the automatic invite feature IS disabled.

I am using 1.80

Really odd. We'll look into it. However I am not sure what is causing this. 

The picture that thetravellor posted is exactly what I was talking about, I can accept invites and give out invites without OQ or anything. This is directly an Oqueue problem I believe. :/