I tried installing and configuring the WP plugin for Zoho Subscriptions but cannot get it working.  Following the directions on the integrations page, I end up with the below after creating a new page, clicking the button to add the Subscription and selecting the plan.  The page shows blank when browsing.  WP version 5.4.

<iframe id="ZSubscriptions" style="border: none;" src="https://subscriptions.zoho.com/subscribe/a64cdba7b185214a8d7e3db7206fd5141f563cd205dd5841ad482bf477cf719e&lt;br /&gt; &lt;b&gt;Warning&lt;/b&gt;: Cannot modify header information - headers already sent by (output started at /home/thesta15/public_html/optimizeforoutcomes.com/wp-content/plugins/zoho-subscriptions/zs-settings-update.php:38) in &lt;b&gt;/home/thesta15/public_html/optimizeforoutcomes.com/wp-admin/includes/misc.php&lt;/b&gt; on line &lt;b&gt;1259&lt;/b&gt;&lt;br /&gt; &lt;br /&gt; &lt;b&gt;Warning&lt;/b&gt;: Cannot modify header information - headers already sent by (output started at /home/thesta15/public_html/optimizeforoutcomes.com/wp-content/plugins/zoho-subscriptions/zs-embed-checkout.php:16) in &lt;b&gt;/home/thesta15/public_html/optimizeforoutcomes.com/wp-admin/includes/misc.php&lt;/b&gt; on line &lt;b&gt;1259&lt;/b&gt;&lt;br /&gt; /0001" width="700" height="900"></iframe><script type='text/javascript' src='https://www.optimizeforoutcomes.com/wp-content/plugins/zoho-subscriptions/assets/js/zs-height-custom.js'></script>