free trial form (on this site https://ahall889.wixsite.com/unidoc) needs to send a web request to our webservice to activate the trial, it can return error messages. Can wix send to a custom web service and handle the errors and pop up if error?
Will api work like this ? Velo: Accessing 3rd-Party Services with the Fetch API | Help Center | Wix.com
You will need to read about how to access 3rd party services in the article Corvid: How to Access 3rd-Party Services with the Fetch API .
Take a look at the Advanced examples , many of them access 3rd party services. A couple of good examples to start with are: Example: Using the Places API from Google Maps services and Example: Send email with the SendGrid REST interface .