Bug fix Contact Form 7
Problem: Contact Form 7 doesn’t send message in Firefox, and in Google Chrome all right.
Solution: Open Firefox console, Network Tab we can see next message:
(POST feedback) {"code":"shield_block_anon_restapi","message":"Anonymous access to the WordPress Rest API has been restricted by Shield.","data":{"status":401}}Reason for that behavior the plugin Shield Security and enabled Anonymus REST API option, to be exact. For fixed that need go to Shield Security - Lockdown - API & XML-RPC - Anonymus REST API and set Disable.