Thank you.
This is very strange. I suspect your server cache, as the JSON-API responses are normally cached for a few seconds using transients. If you can, please try the following:
1. In Wallets -> Exchange -> JSON API -> “Seconds to memoize market API calls”, try setting this to 0. It will disable caching of the JSON API response. Does the market appear in the frontend after this change?
2. Clear your server-side object cache (w3 total cache, memcached, etc) It’s a long shot but worth a try.