website crashes when activating WC Fields Factory

When I activate WC Fields Factory (v2.0.8), my site crashes, showing a 500 error. I’ve tried replacing the wcff fields php file, as instructed here, but it didn’t work: https://www.ads-software.com/support/topic/v-2-0-0-update-error/

I’m working with
WP 4.9.6
WooCommerce 3.4.2
PHP 7.2, 7.1, 7.0

Any help would be greatly appreciated.

Thanks.