Need to add space to my sign-up page because it doesn't display in total

We have a sign-up page for our customers that is hidden in the nav panel, just is accessible via link embedded into certain pages of the site. When you click the link to sign-up for an account, the mobile version isn't displaying the sign-up page form in totality. It cuts off about 4 fields from the bottom. I need to add more space to that code. How can I go about doing that?

https://www.ommovementstudio.com/account-sign-in

That's the link, in mobile the entire form under "sign up for an account" isn't viewable.

Where are you getting the code for the signup form?

It's from our customer platform, Zingfit. It doesn't happen on the web version but it's happening on the mobile version. 

Can you share the code here?

Absolutely!

<iframe src="https://ommovement.zingfit.com/reserve/index.cfm?action=Account.info&site=1&st=c52a52ba-0a3a-485d-a74f-9f81e0dabfd7&initialWidth=1328&childId=zingfit-embed&parentTitle=Schedule%20%E2%80%94%20OM%20Movement&parentUrl=https%3A%2F%2Fwww.ommovementstudio.com%2Fschedule%2F%23%2Faccount" width="100%" scrolling="no" marginheight="0" frameborder="0" height="1400px"></iframe>
                    

Just iframe but that solved the issue. THANK YOU!