Clojurians Log v2

Hello. What could be the case when pod.huahaiy.datalevin/transact! returns nil? As I see from code there is nil return from get-cn function. But what can be the cause of it? And cn in my case is definitely set to something like #:pod.huahaiy.datalevin{:conn #uuid "c65ed6ba-e209-4ece-9dff-835cf2aa7b4c"} https://github.com/juji-io/datalevin/blob/c646d83a2c9fed585581319855218d12af65220f/src/pod/huahaiy/datalevin.clj#L235