Hello @sam104573 if your website has received a high amount of login attempts (successful or not) the file where the plugin logs this information will become too big to be handled by the PHP interpreter. I have fixed this issue with commit #02839f5 [1] by adding a pagination. However, if your hosting provider has set a very low memory limit you will still have problems with the execution of this page. I suggest you to ask them for assistance maybe increasing the memory limit.
Marking as resolved, feel free to re-open if the issue persists.
[1] https://github.com/Sucuri/sucuri-wordpress-plugin/pull/29/commits/02839f5