A 503 status code refers to the Service Unavailable error. This might be thrown by a web server when it is not ready to serve any requests at the moment. This status code also means that there aren't any issues with the server but it is just not ready to serve your request. It might be caused by resource exhaustion or the server being down for maintainance.
You can solve this error by figuring out if the server is actually down for maintenance or whether it is just not responding specifically to your requests. If it is the former, then waiting for a while before trying again might solve the issue. However, it it is the latter, make sure you are using undetected-chromedriver or a similar tool and pairing it up with proxies from a reliable proxy provider like ScrapingBee. Or better yet, use ScrapingBee's web scraping API and let us handle the task of getting around the 503 error. This should help solve the issue.