Reply To: How to edit Multi-Currency botton

It is likely your theme is overriding the CSS. You can do the following test to isolate:

Test for Plugin and Theme Conflict Before Posting an Issue or a Bug

You can try using the !important tag to see if you can force the CSS to take. See the example below:

.asp-multicurr-select{
    font-size: 20px;
    color: red;
    padding: 15px !important;
}