Same issue as @alex_at_twofive25_dot_com and @CharlesTWM
Testing with iOS 16.5 failed, but iOS 14.8.1 was successful. The following are the differences I observed in the device logs.
iOS 14.8.1
com.apple.IdentityLookup.MessageFilter Connection 13: connected successfully
com.apple.IdentityLookup.MessageFilter Connection 13: TLS handshake complete
com.apple.IdentityLookup.MessageFilter Connection 13: ready C(Y) E(Y)
com.apple.IdentityLookup.MessageFilter Task <BD3610F1-17C9-408B-8BD9-36760810BC60>.<1> now using Connection 13
com.apple.IdentityLookup.MessageFilter Connection 13: received viability advisory(Y)
com.apple.IdentityLookup.MessageFilter Task <BD3610F1-17C9-408B-8BD9-36760810BC60>.<1> sent request, body S 810
com.apple.IdentityLookup.MessageFilter Task <BD3610F1-17C9-408B-8BD9-36760810BC60>.<1> received response, status 200 content K
com.apple.IdentityLookup.MessageFilter Task <BD3610F1-17C9-408B-8BD9-36760810BC60>.<1> done using Connection 13
iOS 16.5 (print log only at first time and receiving external server response)
com.apple.IdentityLookup.MessageFilter Connection 1: connected successfully
com.apple.IdentityLookup.MessageFilter got event: Connection invalid
com.apple.IdentityLookup.MessageFilter Connection 1: TLS handshake complete
com.apple.IdentityLookup.MessageFilter Connection 1: ready C(Y) E(Y)
com.apple.IdentityLookup.MessageFilter [C1] event: client:connection_reused @0.160s
com.apple.IdentityLookup.MessageFilter Task <8025DB62-2606-44F7-9502-1E68FCA8A5B0>.<1> now using Connection 1
com.apple.IdentityLookup.MessageFilter Connection 1: received viability advisory(Y)
com.apple.IdentityLookup.MessageFilter Task <8025DB62-2606-44F7-9502-1E68FCA8A5B0>.<1> sent request, body S 1766
com.apple.IdentityLookup.MessageFilter Task <8025DB62-2606-44F7-9502-1E68FCA8A5B0>.<1> received response, status 200 content K
com.apple.IdentityLookup.MessageFilter user sessions enabled, targeting 501
com.apple.IdentityLookup.MessageFilter cleaning up unpooled xpc conn to trustd 0xc2290faa0
com.apple.IdentityLookup.MessageFilter got event: Connection invalid
com.apple.IdentityLookup.MessageFilter Initializing connection
com.apple.IdentityLookup.MessageFilter Task <8025DB62-2606-44F7-9502-1E68FCA8A5B0>.<1> done using Connection 1
iOS 14.8.1 print following log in the end, but iOS 16.5 doesn't
com.apple.IdentityLookup.MessageFilter Connection 13: done
How can I identify the root cause of the error message: "got event: Connection invalid"?