warning after website update

I am having the same warning on a production site with a bbPress forum, except it is also preventing the page from loading correctly. Our forum root is set to show Topics by freshness:

https://www.cashflowdepot.com/community/

Page 1 & page 2 work ok but page 3+ are not accessible. They display “Oops, restricted content”.

https://www.cashflowdepot.com/community/page/3/

When I access the site on a staging server set to expose errors I also see:

Invalid argument supplied for foreach() in /nas/content/staging/cashflowdepot/wp-content/plugins/woocommerce-pay-per-post/public/class-woocommerce-pay-per-post-public.php on line 368

Interestingly, if a user is browsing a specific forum (rather than all forums) all of the pages work:

https://www.cashflowdepot.com/community/forum/creative-real-estate-discussions/page/3/

In a staging environment with WP 4.9.8 I switched to Twenty Seventeen 1.7 and deactivated all plugins except:

bbPress 2.5.14
WooCommerce 3.4.6
WooCommerce Pay Per Post 2.1.13

..and the problem persists.

In the actual class-woocommerce-pay-per-post-public.php file on line 368 can you replace

foreach ( $product_ids as $id ) {
with

foreach ( (array) $product_ids as $id ) {

And see if that removes the warning messages for you.

Thank you. This removes the PHP warning from bbPress and BuddyPress but does not resolve the conflict with bbPress.