If your website suddently goes down, even if you have not made any changes or updates for months, follow these troubleshooting methods to try and restore it to regular service.
Is the entire website down? Are there only a few locations or pages that are throwing an error message? Do you have the same trouble in all website browsers?
Usually there are connectivity issues somewhere between your machine and the server. If you cannot bring up any other website, the trouble is with your local Internet connection though occasionally certain IP ranges in different locations can become blocked.
If none of the previous steps provided any information, there was likely some sort of update that caused the problem.
If you have not touched your website files, make sure no one else has.
Check to see if updates to Apache, PHP, MySQL, your site application(s), or other programs have been applied.
Software like WordPress, Joomla, and more are frequently vulnerable to hackers, but it may not always be easy to spot the attack since they want to retain long term access.
Never rule out hardware issues like corrupted disks or memory. If possible test a blank setup in another directory or account on that server to try and trigger the same errors.
Where possible and necessary, you will want to update or tweak your tools to get things working again. Support cannot modify your code for you, but we can try to guide you through the above steps to help you find a resolution.