The Krunker website uses AJAX calls.
Solution
To click on the element Register you need to induce WebDriverWait for the element_to_be_clickable() and you can use the following locator strategies:
driver.execute("get", {'url': 'https://krunker.io/'})
WebDriverWait(driver, 20).until(EC.element_to_be_clickable((By.XPATH, "//button[@id='onetrust-accept-btn-handler']"))).click()
WebDriverWait(driver, 20).until(EC.element_to_be_clickable((By.XPATH, "//div[@id='signedOutHeaderBar' and contains(., 'Login or Register')]"))).click()
WebDriverWait(driver, 20).until(EC.element_to_be_clickable((By.XPATH, "//div[@class='accBtn button buttonP' and text()='Register']"))).click()
Note: You have to add the following imports :
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions as EC