admin-ajax.php 505 error when submit password

Hi,
Plugin stopped working. When I typed password, it’s doesn’t work.
I have done inspect element and in the console it showes …..admin-ajax.php 500 error.

You can on the link I added. http://i.prntscr.com/D3ICyxDpS9qerGBSp0QLhw.jpeg

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