Devo 7 THSTK Beeping Error

Hello,
Just got a Runner 250 with a Devo 7 as a gift.
The first day we took it out, it had the flip problem. The person who bought it for me tried to adjust some things but that did not work.
The next day I plugged the Runner 250 in (without the props on) before turning on the Devo 7. When it could not connect, I shut both and restarted in the correct manner. At that time, did not notice if it was beeping or not.
When I restarted both, the Devo 7 displayed THSTK and would continue to beep until I pushed the RIGHT SIDE throttle stick all the way down. The beeping would stop and the display flashed RUNNE then TH 50%. When the Runner connected, the engines were spinning quite fast (guessing at 50%). Even if I brought the RIGHT SIDE Throttle all the way down, the engines were still spinning (guessing they were running the other way..)
I think the TH should be at 0% when its in the middle.. but I am a newbie so unsure if this is correct or not. I only tried to fly it for like 2 seconds and it flipped. But I did seem to think the prop motors were controlled by the left side.
Spent at least 5 hrs reading the manual, watching videos, etc. Tried to re-calibrate. At this point just frustrated. Help Please!

Hi FDR, thanks for the reply.
According to the directions in the Runner manual, the tx should be setup in Mode 1. That's how it was first setup and the left stick was controlling the throttle.
I read in the manual how to change from right hand throttle to left. It says you have to open the back and make a mechanical change, as well as a config change. Since we did not open the back, I have no idea how it switched. The gift giver may have mistakenly changed a config setting when he was trying to fix the "flip of death".
But I did reset the runner config on the tx a few times, followed instructions to re-add, but same thing.
I will try to setup the runner config under Mode2 and see if that helps.
Thank you for your advice.