One of our Appsync is not working

Problem statement :— We have built many Appsync(15 approx). One of our appsync which was working earlier is now showing issues. There is no data issues related to it and no error found. The data is flowing in the appsync through the IOT core, the params are getting created properly and passed to the appsync client, which is able to execute it but there is no data getting shown when we see through the appsync. Because of this UI is not able to see any data and there is no error in the UI also. We have also tried to diagnose it by enabling the x-ray deamon to trace the error but no error encountered. All statements above and below to appsync client is executing well. Response of the mutation, we are receiving as { "data": { "mutation_name": null } }, it We double checked our resolver configuration as well, it looks fine also the same resolver is being used by many of our other mutations which are working fine. We haven’t faced any such issue and seek your support now to fix.

The strange thing Is that it has stopped working even in our test and prod environment after few days without pushing any changes to both env as our code is in freeze state.

Note :— Our all appsync are almost similar.

Process :—

ECS — IOT core— lambda — appsync — timestream — UI screen

If you need more information let us know. We expect a quick fix.