I can't accept alert in selenium python

I know there are already a lot of answers, but non of them worked for me.

The alert, that I want to accept looks like this: https://i.stack.imgur.com/BB1Zz.png

It's the alert that show's up, when you try to add a new Chrome-extension.

This is my code:

        subprocess.Popen(r'cu2\chrome'+str(this_task)+'.bat')
        time.sleep(3)
        options = Options()
        options.add_experimental_option('debuggerAddress', 'localhost:'+str(this_port))
        browser = webdriver.Chrome(options=options)
        browser.get('https://chrome.google.com/webstore/detail/proxy-helper/hheejnkdpbnlbppabadgboahgjdikacj?hl=de')
        
        time.sleep(4)
        add_ext = browser.find_element_by_xpath('//*[@class="g-c-R  webstore-test-button-label"]')
        add_ext.click()
        time.sleep(8)
        alert = browser.switch_to_alert()
        print(alert.text)
        time.sleep(3)
        alert.accept()

This is the error, that I get:

selenium.common.exceptions.NoAlertPresentException: Message: no such alert