Gravity forms Name fields not being sent

I’m using Gravity forms to post a form using JSON but the fields for first and last name aren’t being posted. I’ve got the fields mapped using the GF input names (input_1.3 for first name, and input_1.6 for last name) but the post is not including them.

Here’s a screenshot of my mapping: https://imgur.com/dF1o04l

Here’s the HTML snippet from my form:
<input type=”text” name=”input_1.3″ id=”input_1_1_3″ value=”” aria-label=”First name” aria-required=”true” aria-invalid=”false”><input type=”text” name=”input_1.6″ id=”input_1_1_6″ value=”” aria-label=”Last name” aria-required=”true” aria-invalid=”false”>

And here’s the info from the debug email where those fields aren’t being included:
**SUBMISSION**
Array
(
[timeout] => 10
[body] => {“email”:”[email protected]”,”phone”:”(123) 123-0000″,”description”:”testing”,”useragent”:”Mozilla\/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/72.0.3626.119 Safari\/537.36″,”webreferrer”:”https:\/\/example.com\/confirmation\/”,”REFURL”:”https:\/\/example.com\/news\/”,”IP_Address”:”100.00.00.00″,”GCLID”:”testingtesting”,”BINGID”:””,”Contactsource”:”Web Site”,”generator”:”001f400000FRcNvAAL”}
[headers] => Array
(

Thank you in advance for any insight.

Tim