Where are you seeing this error message? In WordPress or in Sendible?
WordPress doesn’t come with any Sendible feature or integration.
Someone, possibly Sendible themselves, did some work to integrate Sendible with WordPress… allowing you to send messages from Sendible to WordPress. Now you’re unable to (properly) send messages from Sendible to WordPress.
In other words, the integration work done by Sendible isn’t working properly, at least not on your website.
It should then logically follow that the problem lies with whatever “work” was done to integrate the two systems. And the responsibility should fall on whoever did this “work” or integration.
In Sendible
So there’s an error message in the integration code written by Sendible. And it’s someone else’s responsibility to troubleshoot their error message and fix it?
Now, I understand that the integration may be working for others, and something on your site may be preventing this integration from working on your site.
But then again, we’re talking about custom integration code written by a Sendible, with error messages appearing in Sendible’s application.
So how can 3rd-parties who don’t have access to the Sendible integration or codebase troubleshoot this?
At the very least, Sendible should be able to troubleshoot their error message (that is appearing in their application), and tell you/us what this error message implies and/or what changes need to be done on your site to clear it.
My thoughts were the same…. which is why I spent some time going through it with their 2nd line support on a zoom call… I could send many exchanges but this is the upshot of it…
From Sendible:
As discussed on the call the message of “Object reference not set to an instance of an object” that can be seen within the Undelivered section of your Sendible account is a message being returned directly from your WordPress site.
After some investigation it does look like the posts are going through to your account as intended, however, the error message is being returned as the generation of thumbnails on your posts do not seem to generate as intended.
As suggested on the call, it would be worth contacting your Theme provider to see if any settings you are missing could auto-generate a thumbnail preview for you. However, they may also suggest there would be a different plugin for you to use.
As mentioned, however, the role of Sendible is functioning as intended with the posts arriving on your WordPress site.
From the theme provider:
This is not a theme issue. Try installing a plugin like this: https://wordpress.org/plugins/wordpress-seo/
From Sendible:
Thanks for the update and sorry to hear that the theme makers were not much assistance.
As mentioned previously the role Sendible plays in this is functioning as intended. Our contribution to this workflow is to publish content from Sendible to your WordPress which is functioning as intended.
However, sadly something seems to be amiss on your site that is then causing the post to not display as you would like (in regards to thumbnails for the post).
I truly wish I could assist further on this, however, as I said on the call I'm a Sendible expert and sadly not a WordPress expert.
——
So I don’t really know where to do now?
Further to that… they were not able to replicate the problem when they tried numerous tests on their own WP sites…