can not apply changes in styles of subscribe form

really weird situation

trying to change the way my subscription form looks and styles doesn’t apply.
my form in a row of three widgets (text) in footer. i were able to make letter uppercase but when i trying to change font-size in the same style it’s doesn’t change.
also trying to change font color on subscribe – button and doesn’t apply too.

and I am kind of sure that i am using right elements

https://www.ads-software.com/plugins/mailchimp-for-wp/