Test script not working [Selenium]

So, I've been tasked with trying to create end-to-end cases with Selenium, but I ran into a problem.

I've taken the xpath of a dropdown and used it as such (changed due to confidentiality):

WebElement DD1 = driver.findElement(By.xpath("//*[@id=\"6394662b1703a4ad7d9dc37c54dc9787_value\"]"));
Select DD = new Select(DD1);
DD.selectByVisibleText("1st Selection");

Nothing happened.

Tried a different one.

Select DD1 = new Select(driver.findElement(By.xpath("/html/body/div[1]/main/div/div[2]/div/div/div/div/div/div[2]/div/div[1]/div/div/div/div[1]/div[1]/div/div[2]/div")));
DD1.selectByVisibleText("1st Selection");

Still nothing.

Then I tried Katalon Studio. The tool was able to use the dropdowns, but it failed when looking for checkboxes.

Any help is appreciated and I will give as many details as possible upon request.

Thanks