In your case you need to make overlay element invisible forcefully before going to click on submit button as below :-
#first make overlay element invisible
overlay = driver.find_element_by_css_selector("div.modal-overlay")
driver.execute_script("arguments[0].style.display = 'none'", overlay)
#now find submit button and click
driver.find_element_by_id("DeleteSurveyOK").click()
Edited1 :- If still it throws exception that submit button is invisible, you should try using WebDriverWait
to wait until submit button visible after overlay element invisible as below :
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
#first make overlay element invisible
overlay = driver.find_element_by_css_selector("div.modal-overlay")
driver.execute_script("arguments[0].style.display = 'none'", overlay)
#now find submit button and click
button = WebDriverWait(driver, 10).until(
EC.visibility_of_element_located((By.ID, "DeleteSurveyOK")))
button.click()
Edited2 :- If unfortunately submit button is not getting visible try to submit form instead of clicking submit button as below :-
#first make overlay element invisible
overlay = driver.find_element_by_css_selector("div.modal-overlay")
driver.execute_script("arguments[0].style.display = 'none'", overlay)
#now submit the form
driver.find_element_by_id("ModelSurveyForm").submit()