Hi Eric,
This is not documented at this time but I have included the list of error codes.
The reason for this is that the error codes are internal statuses that are more relevant for the MongoDB engineering team to investigate the server-side component of Realm Sync. If you have any issues with sync, it would be best to open a chat or ticket directly with the MongoDB Support team: Cloud: MongoDB Cloud.
Please know that the list below is subject to change and may not be consistent in the future.
ErrorCode = 100 // Connection closed (no error)
ErrorCode = 101 // Other connection level error
ErrorCode = 102 // Unknown type of input message
ErrorCode = 103 // Bad syntax in input message head
ErrorCode = 104 // Limits exceeded in input message
ErrorCode = 105 // Wrong protocol version (CLIENT) (obsolete)
ErrorCode = 106 // Bad session identifier in input message
ErrorCode = 107 // Overlapping reuse of session identifier (BIND)
ErrorCode = 108 // Client file bound in other session (IDENT)
ErrorCode = 109 // Bad input message order
ErrorCode = 110 // Error in decompression (UPLOAD)
ErrorCode = 111 // Bad syntax in a changeset header (UPLOAD)
ErrorCode = 112 // Bad size specified in changeset header (UPLOAD)
ErrorCode = 200 // Session closed (no error)
ErrorCode = 201 // Other session level error
ErrorCode = 202 // Access token expired
ErrorCode = 203 // Bad user authentication (BIND, REFRESH)
ErrorCode = 204 // Illegal Realm path (BIND)
ErrorCode = 205 // No such Realm (BIND)
ErrorCode = 206 // Permission denied (STATE_REQUEST, BIND, REFRESH)
ErrorCode = 207 // Bad server file identifier (IDENT) (obsolete!)
ErrorCode = 208 // Bad client file identifier (IDENT)
ErrorCode = 209 // Bad server version (IDENT, UPLOAD, TRANSACT)
ErrorCode = 210 // Bad client version (IDENT, UPLOAD)
ErrorCode = 211 // Diverging histories (IDENT)
ErrorCode = 212 // Bad changeset (UPLOAD)
ErrorCode = 213 // Superseded by new session for same client-side file (deprecated)
ErrorCode = 214 // Partial sync disabled (BIND, STATE_REQUEST)
ErrorCode = 215 // Unsupported session-level feature
ErrorCode = 216 // Bad origin file identifier (UPLOAD)
ErrorCode = 217 // Synchronization no longer possible for client-side file
ErrorCode = 218 // Server file was deleted while session was bound to it
ErrorCode = 219 // Client file has been blacklisted (IDENT)
ErrorCode = 220 // User has been blacklisted (BIND)
ErrorCode = 221 // Serialized transaction before upload completion
ErrorCode = 222 // Client file has expired
ErrorCode = 223 // User mismatch for client file identifier (IDENT)
ErrorCode = 224 // ErrorSessionsLimitExceeded
ErrorCode = 225 // Changeset contained an invalid schema change (UPLOAD)
Regards
Manny