I get an error when trying to subscribe:
Uncaught SyntaxError: Unexpected token T in JSON at position 0
at JSON.parse (<anonymous>)
at XMLHttpRequest.xhr.onload (acymailing_module.js?v=5109:256)
Joomla 3.9.11, php 7.3.9, Acymailing 5.10.10
Other times is takes a lot of time (few minutes) until it displays the messages (using ajax) or redirecting to another page.