Got the same problem (I think). In a PBEM game my opponent resigned. I hit the review button, and got an error (unrecognized matrix server respons, via point 24) pop up, and after it this text:
Body = {"InstanceID":"91957","ThisSideNum":"1","Viewed":"True"}
ERROR: Response = {"Message":{"ErrorCode":29,"ErrorComment":"You are not in this challenge","DebugMessage":"Player not in this instance with this side num"},"Result":false}
25> Download Instance 91957 File: (StepNum = 11)
Breadcrumb: 25
ErrorCode = 200
Resource = /instances/files/igougo/91957
Body = < Empty >
ERROR: Response = {"Message":{"ErrorCode":0,"ErrorComment":null,"DebugMessage":null},"Result":{"SideNum":1,"UserID":45971,"StepNum":11,"UpdateDateTime":"2022-11-29T15:16:47+00:00"}}
25> StepNum: 11
25> File loaded OK
24> Set Instance 91957 (Final) Viewed State:
24>Error Code 29
24>Error Comment You are not in this challenge
24>Debug Message Player not in this instance with this side num
Breadcrumb: 98
ErrorCode = 29
Resource = /instances/viewed
Body = {"InstanceID":"91957","ThisSideNum":"1","Viewed":"True"}
ERROR: Response = {"Message":{"ErrorCode":29,"ErrorComment":"You are not in this challenge","DebugMessage":"Player not in this instance with this side num"},"Result":false}
Looks to me as if the game either didn't switch to my side, didn't give permission to both sides to see the end result, or closed the game prematurely, so there are no users with permission to view it... But when I progammed last, the Motorola68000 was state of the art, so it could be something totally different

.