Typically this error is only temporary and may resolve itself, and it means what it says specifically in that the server is temporarily unable to handle the request. However, it is functioning as usual otherwise.
503s predominately occur if the server is undergoing maintenance or it is too busy in general.
To start, try the URL again or press F5 or Ctrl+R refreshing the page and calling the server again.
If this does not work, and though it is improbable, it may have something to do with your router or modem. If you see Service Unavailable - DNS Failure error, this is more likely the case. Try restarting your router and modem, and then do the same with the device you are using as well.
In cases, make sure that your scripts, software, plugins, and themes are functional, as when poorly coded, these can be common root causes. Note that if you have installed new software such as plugins and themes, you may have to remove or update it.
If the traffic to your site suddenly spiked and your system has come under a heavy traffic load, that may prevent the server from properly serving all incoming requests. The server itself has not crashed or shut down but has instead set itself to a mode of service that will prevent any additional requests from being served as usual.
If something has stopped working correctly, or you're simply running out of resources, you may need to consider upgrading your resources.
If the troubleshooting steps here fail and the error does not go away, please get in touch with our technical support team by live chat or opening a ticket and we'll help you get to the bottom of it.
It is worth noting that malicious denial of service (DoS) attacks can also result in 503 errors. Hostwinds provides DDoS protection addons that are available at any time.