Multi Wire circuit breaker won't reset

I have a multi wire circuit breaker that won't reset. Nothing is plugged into the outlets for this breaker. It is probably my own fault, but I would like to get opinions.
There was an available circuit breaker in the panel. I ran wires to this available circuit breaker for a new outside outlet.
Being the novice that I am, I failed to turn off the Main. I had to double up the ground wire for this new circuit, with an existing ground wire. I did not add it to the ground wire of the now bad Multi wire ckt. breaker.
I added the white common wire to it's own slot.
Is it possible just by adding these wires to the ground bar that I could have made this Multi Wire ckt. breaker go bad?
thanks for any ideas you might have. I have not yet replaced the breaker, but I now know to turn off the Main if it comes down to that. thanks.

Greetings gg welcome to the Forum.

I presume what you're talking about is a 2-Pole Resettable Breaker, for a 220 volt circuit.

It is not necessarily required that you turn the mains off, to handle breakers.
You can unsnap them from the Box, do your connections, then, snap them back in.

If you pull the Breaker out of the Box, can it be reset then ?

Have a good Day !
S.W.

Thank you for the response - I will try that tonight. It is actually a Ground fault 20 amp breaker I found out. Someone told me I might have doubled up the ground on this GF breaker, and that you cannot do that. Would you know if the ground can be shared on the GFCI or AFCI circuit breakers? thanks again!

this AFCI breaker would not turn off or on. I disconnected all 3 wires, then I could turn it off. Reconnected all 3 wires, and now it is working fine. Thanks for your help SW.