Your wordpress website theme become corrupted. This might be an extremely frustrating situation. But fortunately there are many ways to restore your website theme. But let us see what happens when wordpress theme becomes corrupted and what are the solutions.
1- No further theme updates
Your theme has becomes corrupted because it might had become old or the theme publisher had stopped providing updates for it. In such case you should change the theme.
2- Theme not updated
You forgot to update your theme. Perhaps your theme got corrupted because it had not been updated for a long time. Try updating your theme and see if it works.
3- WordPress version too old
Your current wordpress version might be too old. Check for any new updates. Doing this might solve the issue.
4- Incompatible plugins
You have installed some new plugins which might be interfering with theme files. If this is the case, then you should disable and delete the faulty plugin.
5- Incorrect or wrong code saved
Perhaps you have changed some of the codes in the theme files, which caused your site to go down or offline. This can be a serious problem to solve. To solve this problem you have to log in to your cpanel and undo the changes you have made. Just open the file in which you have made changes and correct the code, which is causing error.
6- Unknown reasons
If your website had become corrupted due to unknown reasons then you can restore the previous website backup. There is one great advantage of restoring backup. Your website will become as it is like that of before. You can use popular wordpress backup plugin like Updraft plus.
7- DDOS Attack
May be DDOS attack had made changes in your wordpress core files. Always use good security plugins such as Wordfence to prevent DDOS and other attack on your website. You can also manually block the suspected IP. Wordfence premium have also other unique features.