WordPress Photo Gallery

Hello,
I got a problem which is appered when I try to download one album by this link ( gallery.supersprox.eu/wp-admin/admin-aja…gallery&gallery_id=1 ) from my website-gallery, which is working on WordPress 4.8.3 we get an error The site gallery.supersprox.eu not process this request yet HTTP ERROR 500. In album inside 496 photos. Before it worked properly, maybe we reached some restrict quantity of pictures or volume of space which allow to download this plugin or maybe something more… Could you give to us, please, some adwises for how to fix this problem ?
Thank you in advance !

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