I'm not sure if the Curl action in ChronoForms v5 is intended to work the same way as the cURL[GH] action in ChronoForms v4 but it doesn't seem to work quite the same way.
Here is a start to finish tutorial on how I managed to enable an AcyMailing subscription using cURL in ChronoForms v5.
In my form the Newsletter subscription is optional but ticked by default:
Webilicious Web Design and Development
I forgot to mention that if you have enabled Captcha in AcyMailing you also need to include the security key in the Target URL" field like this:
Update: Please ignore the issue I posted above. I worked out there is a typo in a field name in the Custom Code which should be "ParentGuardianSurname" rather than "ParentGuardianSurame".
That's what you get when you stare at the same code for too long!
Just as a matter of taste I prefer not to add parameters in the target URL but to pu them all in the Fields/Params box - I do understand though that the behaviour of the standard action doesn't encourage that :-(
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