could you check and provide sync gateway logs? It’s hard to tell what happened based on what you described, but please check the following:
verify if sync gateway service is up and running, I am not sure what OS the sync gateway is deployed, please get the command for the OS and check sync_gateway service status
get sync gateway logs. in your sync gateway deployed location, pull sg_error.log under logs subdirectory
it’s possible there is something wrong in sync gateway config, or there is an issue to connect to your couchbase server. bucket name, user credential, certificates may be other things to check.
what was the last known working version? 2.7.x? you mentioned about 2.8.0 and 2.8.3, with both the versions, you have experienced the hanging issues, is that right?
The /_changes API results when not cached by Sync Gateway are backfilled using a request plus view or query run on Couchbase Server, it’s possible that query was taking an abnormally long time to return results back to SG, which could be for a number of reasons given the request plus consistency level.