When attempting to load attachments larger than 1Mb fail to be uploaded, no error messages are captured in the log files. Fiddler will show an error similar to:
HTTP/1.1 413 Request Entity Too Large
Date: Tue, 31 Jul 2018 13:52:33 GMT
Service Desk 14.1 or higher
Internet Information Services
LoadBalancers (nginx or others)
The load balancer that is referenced in the Fiddler trace "Server: nginx/1.14.0" had configured the client_max_body_size to 1Mb causing that higher values wont be able to pass through it.
The error "HTTP/1.1 413 Request Entity Too Large" is a generic error and it wont specify which server caused the error using Fiddler or other proxy tools can help to find out the root cause.
In the load balancer update the value for the setting client_max_body_size which by default is set to 1Mb and set it to the necessary size.