Subscribe button is only half background

https://paste.pics/145c25177d787c25f12d8c1c3eb5aa4d

As you can see the subscribe button background is only half. How do I fix this?
I have used this code

<div class = “row”>

<div class = “col-md-3”>
[text* Your-name placeholder “Name”] </label>
</div>

<div class = “col-md-3”>
[text* Your-email “Email”] </label>
</div>

<div class = “col-md-3”>
[submit “Subscribe”]
</div>

</div>