It is reported that only one user is receiving this error when trying to access the Attachments screen on an Incident:
<Attachment Server URL> sent an invalid response
Release : 17.3
Component : SDM - Attachments
Because this is reported for only one person a number of items could cause this issue:
Network Issue
Certificates not present (If SSL is configured)
System Specific issue
End user was unable to upload attachments and received a " <Attachment server URL> sent an invalid response"
It was discovered that the customer was not using VPN.
Check the nx.env for the attachment server setting if the issue is more widespread
Because the issue is only reported for one user instead of many, it may be better to focus your investigation on the individual user first