Something wrong happened while you were using a plugin in WordPress (freeze, or something similar) or your website is crashing with a blank screen, or anything else?
Checking your PHP Error Logs is the first reaction you should have. The PHP Error Logs is not the Access Error Logs (which is the error related to your web server and not PHP).
You can access them through the admin given by your hosting service (not the WordPress one). Depending on your hosting service, they can also be accessed by an additional plugin (Error Log Monitor (Error Log Monitor) or even the Meow Apps Dashboard (at the bottom right on it you will find a link to your logs). They contain errors related to programming errors but also memory, space, and execution time issues.
Please note that the PHP Error Logs is rarely empty. Unfortunately, PHP Error Logs are not always accessible. If you find an empty file or no file at all, the logs might be disabled. Ask your hosting service to make sure. You must know if your logs are really working otherwise you will always have issues and never know where they come from.
There is an additional thread on StackOverflow where people are discussing this, have a look here: Where does PHP store the error log?
You will need to use Google Chrome. You can do it using other browsers but Google Chrome is the most convenient.
This is an important check, especially when a plugin is performing asynchronous actions (long-running process). Open your Google Chrome’s “Developer Tools” (https://developer.chrome.com/devtools) and click on the Network tab. Starts the process again until the issue occurs. Go back to the Network tab and click on the last request that was executed (the left column) and look to the right window. The Response tab might contain something interesting, like an error, or a broken reply from the server (if it is HTML, that’s also an issue as the message from the server is usually tiny and using JSON format). Please also check the Console window at the bottom, as it might have some interesting information as well.