So this is interesting. Syncing via CloudKit fails, but the Legacy sync works just fine. Unfortunately, I have fallen down on the job recording my Legacy secret key, so I cannot get any of the databases into DTTG 3 
Just as an FYI, Console does report cloudd
errors:
|default|13:27:02.527612-0500|cloudd|Task <B42D87BE-40EC-45DA-B07E-DC02733A5C7C>.<141> {strength 0, tls 4, ct 0, sub 0, sig 1, ciphers 0, bundle 1, builtin 0}|
|---|---|---|---|
|default|13:27:02.528456-0500|cloudd|Connection 1174: enabling TLS|
|default|13:27:02.528501-0500|cloudd|Connection 1174: starting, TC(0x0)|
|default|13:27:02.528542-0500|cloudd|[C1174 3A3E77E7-66D0-43CE-B886-DC8F8027D154 Hostname#8f73a900:443 tcp, bundle id: com.devon-technologies.think3, url hash: cf0e3f3b, tls, context: com.apple.CFNetwork.NSURLSession.{D39853E1-8888-498F-B0D0-CCA2D5850A98}{(null)}{Y}{2}, proc: 4811B1D0-6340-35EE-87F7-6983E3DFEC4F, effective proc: 61DD113A-277A-3B80-A37C-44ACFE229548, no cellular fallback] start|
|default|13:27:02.529191-0500|cloudd|[C1174 Hostname#8f73a900:443 initial path ((null))] event: path:start @0.000s|
|default|13:27:02.529290-0500|cloudd|[C1174 Hostname#8f73a900:443 waiting path (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: path:satisfied @0.000s, uuid: 419842E8-1E81-446E-AC30-409CD9DD0256|
|default|13:27:02.529376-0500|cloudd|[C1174 Hostname#8f73a900:443 in_progress resolver (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: resolver:start_dns @0.000s|
|default|13:27:02.529396-0500|cloudd|nw_connection_report_state_with_handler_on_nw_queue [C1174] reporting state preparing|
|default|13:27:02.529831-0500|cloudd|Task <B42D87BE-40EC-45DA-B07E-DC02733A5C7C>.<141> setting up Connection 1174|
|default|13:27:02.530519-0500|cloudd|[C1174 Hostname#8f73a900:443 in_progress resolver (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: resolver:receive_dns @0.001s|
|default|13:27:02.530798-0500|cloudd|[C1174.1 IPv6#8642efdc.443 initial path ((null))] event: path:start @0.002s|
|default|13:27:02.530920-0500|cloudd|[C1174.1 IPv6#8642efdc.443 waiting path (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: path:satisfied @0.002s, uuid: 20084121-33E0-4CAA-92FA-94FBE38513B8|
|default|13:27:02.532566-0500|cloudd|[C1174.1 IPv6#8642efdc.443 in_progress socket-flow (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: flow:start_connect @0.003s|
|default|13:27:02.539688-0500|cloudd|nw_protocol_boringssl_error(1752) [0x7f9b6daaebc0] Lower protocol stack error pre TLS handshake. [57: <private>]|
|default|13:27:02.539853-0500|cloudd|nw_flow_disconnected [C1174.1 IPv6#8642efdc.443 in_progress socket-flow (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] Output protocol disconnected|
|default|13:27:02.540220-0500|cloudd|[C1174.1 IPv6#8642efdc.443 failed socket-flow (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: flow:failed_connect @0.011s, error Socket is not connected|
|default|13:27:02.540368-0500|cloudd|[C1174.2 IPv4#26bec851:443 initial path ((null))] event: path:start @0.011s|
|default|13:27:02.540482-0500|cloudd|[C1174.2 IPv4#26bec851:443 waiting path (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: path:satisfied @0.011s, uuid: 4F66EA8A-EF97-4555-A630-0C4C72FEBF81|
|default|13:27:02.540925-0500|cloudd|[C1174.2 IPv4#26bec851:443 in_progress socket-flow (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: flow:start_connect @0.012s|
|default|13:27:02.542419-0500|cloudd|nw_protocol_boringssl_error(1752) [0x7f9b6ddde990] Lower protocol stack error pre TLS handshake. [57: <private>]|
|default|13:27:02.542489-0500|cloudd|nw_flow_disconnected [C1174.2 IPv4#26bec851:443 in_progress socket-flow (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] Output protocol disconnected|
|default|13:27:02.542699-0500|cloudd|[C1174.2 IPv4#26bec851:443 failed socket-flow (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: flow:failed_connect @0.014s, error Socket is not connected|
|default|13:27:02.542752-0500|cloudd|[C1174 Hostname#8f73a900:443 failed resolver (satisfied (Path is satisfied), interface: en0, ipv4, ipv6, dns)] event: resolver:children_failed @0.014s|
|default|13:27:02.542773-0500|cloudd|nw_connection_report_state_with_handler_on_nw_queue [C1174] reporting state failed error Socket is not connected|
|error|13:27:02.542795-0500|cloudd|Connection 1174: received failure notification|
|error|13:27:02.542819-0500|cloudd|Connection 1174: failed to connect 1:57, reason -1|
|error|13:27:02.542855-0500|cloudd|Connection 1174: encountered error(1:57)|
|default|13:27:02.542870-0500|cloudd|Connection 1174: cleaning up|
|default|13:27:02.542886-0500|cloudd|Connection 1174: summary for unused connection {protocol=(null), domain_lookup_duration_ms=0, connect_duration_ms=0, secure_connection_duration_ms=0, idle_duration_ms=0}|
|default|13:27:02.542927-0500|cloudd|[C1174 3A3E77E7-66D0-43CE-B886-DC8F8027D154 Hostname#8f73a900:443 tcp, bundle id: com.devon-technologies.think3, url hash: cf0e3f3b, tls] cancel|