Not sure if I should create a ticket here, becuase the culprit seems to be libs/AceDB-3.0 and the source code is not in this repository. Feel free to close it if this issue is inappropriate.

I made it work on my local PTR client by adding

if regionKey == nil then regionKey = "PTR" end

after L263 of libs/AceDB-3.0/AceDB-3.0.lua in OmniCC 10.1.1.

Also the PTR will be closed in 3 days so maybe it's not worth fixing this issue.

Also it might be my local issue, because I remember I did use OmniCC successfully on the early day of 2nd PTR, but it crashes suddenly after a client update.