Is it possible to style an HTML embedded form?

Site URL: https://grtv1.squarespace.com

My client needs to use an embedded form code to have the website user submitted data post to a CRM dashboard they use.

The problem I'm having is that this form looks extremely basic, and it is not responding to any CSS styling that I have tried. 

The form code looks like this (currently NOT on the site link). Can't even see the submit registration link, since it is in white text and just a regular text link without a button:

And my client and I want it to look like this (which I was able to achieve using SS form block with custom CSS. But I can't get the data to integrate to the client's CRM dashboard as it is with a fairly new provider called spark.re. 

So my question is.... will there be anyway to style the code from the first screenshot above, to look like I was able to make the SS form block look?

In case it is helpful, here is the link to the page where I have the HTML code block:

https://grtv1.squarespace.com/home-spark-form-raw-code

Hitting my head against the wall trying to find a solution for this.

No,

You'll need to contact the company who made the widget to get any sort of reliable control over the embed. Just looking at their blog, it looks like their might be some options available through them.

https://blog.spark.re/how-to-set-up-custom-registration-forms-with-social-media-ads-17973d06fa36

That's what I thought too, but Spark folks told me to check with squarespace for customization and that didn't make much sense to me, but I thought I'd ask in case anyone had encountered something similar. I've been in discussion with Spark team, and they don't offer support for customizing the form styling. They would rather the client upgrade to an API feature that then has to link Squarespace form submission --> Zapier --> Spark. A bit clunky, and in this case, the client will just manually enter the form submissions into their Spark CRM, since they are not anticipating extremely high volume of submissions. Hope this info helps someone else sometime!

Yeah definitely seems like overkill for their needs! Good to know about that option in the future though!