Facebook messenger plugin would not close

I just found a solution:

<style>
    .fb_customer_chat_bounce_out_v2 { animation-fill-mode: forwards; display: unset !important; }
    .fb_customer_chat_bounce_in_v2 { display: unset !important; }
    .fb_iframe_widget iframe { display: none; }
</style>

This worked for me.

Until Facebook will fix this bug, you can temporarily fix this by adding display: none to their .fb_customer_chat_bounce_out_v2 class:

.fb_customer_chat_bounce_out_v2 { display: none; }

if you select left direction so you can add this css

<style>
    @keyframes fb_bounce_in_from_right {
        0% {
            opacity: 0;
            transform: scale(0, 0);
            transform-origin: bottom left
        }
        50% {
            transform: scale(1.03, 1.03);
            transform-origin: bottom left
        }
        100% {
            opacity: 1;
            transform: scale(1, 1);
            transform-origin: bottom left
        }
    }
    @keyframes fb_bounce_out_from_right {
        0% {
            opacity: 1;
            transform: scale(1, 1);
            transform-origin: bottom left
        }
        100% {
            opacity: 0;
            transform: scale(0, 0);
            transform-origin: bottom left
        }
    }
</style>