I want to download csv files from \"https://clinicaltrials.gov/ct2/results?cond=&term=lomitapide&cntry1=&state1=&SearchAll=Search+all+studies&recrs=\" we
You are getting the exception ElementNotInteractableException because the element will be accessible after once the popup opens up. You are missing to click the download link which opens up the popup. please try the following,
from selenium import webdriver
fp=webdriver.FirefoxProfile()
fp.set_preference("browser.helperApps.neverAsk.saveToDisk","text/csv")
browser = webdriver.Firefox(fp)
browser.get("https://clinicaltrials.gov/ct2/results?cond=&term=lomitapide&cntry1=&state1=&SearchAll=Search+all+studies&recrs=")
browser.find_element_by_id("save-list-link").click()
browser.find_element_by_id("submit-download-list")