2. Visit the JSON API endpoint
get_coins_info. Use your browser to go to https://example.com/?__wallets_apiversion=3&__wallets_action=get_coins_info (substitute example.com with your own domain). What do you get back? If you don’t get back a proper JSON response, this could mean that there is an issue with caching plugins, the web server configuration, or even something else.
Show me what you found in 1 and 2 and I will advise.