This may be a duplicate from someone else - apologies if it is.
http://manuals.sharkrf.com/openspot3/en/connectors-page.html
states "Note that these custom servers are stored in the browser's local storage (they won't show up using another browser)". Obviously the same would be true if you cleared your browser's cache.
It would be nice to be able to save custom servers in a more permanent way. For example, custom servers could be saved in a profile or directory on SharkRF's server and pulled down to the hotspot. Alternatively, a file could be saved to the local workstation to upload the customer servers. Ideally, the next version of the OpenSpot would have read/write space locally for custom servers and possibly other future features.
73's KI4LTK