NOTE: both of these programs (versions AND instances im using) worked for me with GSA. just checked yesterday and today
my report of captcha breaker:
https://community.bablosoft.com/topic/5896/captcha-breaker-error-error_key_does_not_exist-but-works-with-gsa
Capmonster:

(note it had different msg once, thats when i changed port from default 80 to 90 just for test). so
so it basically seems its connecting to capmonster, but theres an error and captcha is not showing in capmonster.
LOG SENT:
Url: http://127.0.0.3:80/in.php
Method: POST
Content-Type: multipart/form-data; boundary=jyvqkzreyyjjtemicpinbpgddtydmzgdymaeevbj
Accept: */*
--jyvqkzreyyjjtemicpinbpgddtydmzgdymaeevbj
Content-Disposition: form-data; name="method";
post
--jyvqkzreyyjjtemicpinbpgddtydmzgdymaeevbj
Content-Disposition: form-data; name="key";
la123lk21j31lk2j3
--jyvqkzreyyjjtemicpinbpgddtydmzgdymaeevbj
Content-Disposition: form-data; name="file"; filename="image.jpg"
Content-Type: application/octet-stream
����
LOG RECEIVED:
Url: http://127.0.0.3:80/in.php
Status: 200
Content-Length: 5
Content-Type: text/html; charset=utf-8
Server: Microsoft-HTTPAPI/2.0
Date: Fri, 30 Nov 2018 10:54:19 GMT
Connection: close
ERROR