Client can fill out form, but when it's sent back, it's the empty form.

[Jennifer5EC6]

I so appreciate everyone's help so far! 
I am working on a form to email to clients, have them fill out and return it by email.
When I tested it, for some reason, the return email contains only the empty form, no data that they entered.
What am I doing wrong? 
And, when the client receives the form and fills it out, do they need to save it in order to send it back to me? 
Thank you!

[radzmar]

It's not easy to aswer. First we need to know how the receivers open your form and how they send it back to you? What application they use the view the form and is there a button in it they have to click when completed?

[Jennifer5EC6]

Thank you for offering your help. I'm a total nube at this adobe stuff and muddling my way through.
As far as applications go, I'm not sure what each client will be using. Some will use their phones, some will use computers and I'm sure some will have free Adobe and some, who knows. This is a form for (usually) low-income families, so that may guide you a little?
I did not include a button to click when completed as I didn't even know that existed. Is that something that I should include?
The form is to provide their name, address, etc, then a listing of people and animals that are in their home. They ideally, should email that back to me along with several other attachments (photocopy of their driver's license and qualifier, such as a Medicaid card). 
With opening the form, I've just assumed I could attach it to an email, as I've been doing with the fillable form in Word. (which isn't working well, hence why I thought Adobe would work better)

Feel free to offer any and all advice. I'm here to learn.

[radzmar]

The thing is, that PDF is not an Adobe exclusive file format, it's an ISO standard. There are dozens of application that can display PDFs. However, since PDF was enhanced with new features such as forms capabilities, rich media or scripting, it became more and more complex over the years and many of the PDF viewer out there don't support all of those extenstions but a few. So, as long you don't know, what viewer your recepiences use, you can't know, if it will support filling your forms, I'm afraid. I don't see any problems with Adobe Acrobat/Reader, Foxit Reader or PDF Exchange, but with Apples preview, for example (see https://community.adobe.com/t5/acrobat-reader-mobile/my-adobe-pdf-form-appears-blank/td-p/8365298?pa...). 

So in case you got back a blank form, ask the sende about his viewe and how he used it to fill the form. Once you know this, you can start to find a way to solve the problem.