I replaced number 1 motor's esc with a new one of the same brand and value. In BlHeli the new esc shows CH 40 in "esc layout" and the other 3 show CH 15 All other values are the same.

The new one shows BLheli Rev 16.6 while the other 3 are rev 16.00

All 4 motors and esc's work fine in BLheli motor test or in Beta flight.

But when I try to fly the quad when I hit the arm switch, number one motor does not spin and the other 3 do causing the quad to go crazy and flip over forward.

For some reason, the number one esc is not coming on with the other 3 when using the transmitter arm switch. When in Beta flight the arm switch does arm all four esc's and motors spin.
Your thoughts are appreciated.

You should flash them all with lastest firmware and get them all to sync with each other.

"Ch15", "Ch40" i think these numbers indicate different ESC revisions or possibly layouts, this could mean these ESC's are going to perform exactly the same.
Check here:
https://github.com/blheli-configurator/b...ledge-Base

Looks like you might be mixing Aikon 30A V1 and V3, a friend of mine tried mixing V1 and V2 and the quad didn't work until he replaced all the V1 and with V2 because V1 was discontinued.