I am trying to change the thumbnail images as they appear in my Portal's Gallery, (version 10.5). I have worked through the rather straight forward steps to change the thumbnail as outlined in the documentation. Unfortunately this has no effect and my thumbnails remain as the default thumbnails.
When prompted to browse to the file where my image is placed, (on my PC hardrive) and click OK everything seems to work accordingly, (in other words I receive no error messages). My guess is that this process is not really linking or uploading this image to my portal in an accessible way.
Is there an additional process where by I need to upload or link the thumbnail image in ArcGIS Server to make it available to use as a thumbnail in Portal?