403 error when adding new post on the Calendar

[dev]

Hi everyone, we are having issues with the plugin after clicking "+ add post" and selecting "Share your WordPress posts, pages or products" on the calendar tab.

We then get the message "The connection to the server failed. Please try again! You can find more information and solutions in the guide for server connection". I have followed the guide but nothing suggested there has solved the issue.

More specifically, the error appears after the plugin makes this POST call:

 https://logisticsgroupservices.co.uk/wp-admin/admin-ajax.php?_fs_blog_admin=true

But only when it contains this body:

action=b2s_sort_data&b2sSortPostTitle=&b2sSortPostAuthor=&b2sSortPostSharedBy=0&b2sSortPostCat=&b2sSortPostType=&b2sType=all&b2sShowByDate=&b2sPagination=1&b2sShowPagination=1&b2sSortPostStatus=&b2sSortPostShareStatus=&b2sUserLang=en&b2sSchedDate=2023-03-07&b2s_security_nonce=0123456789&b2sPostsPerPage=3

For all other POST requests made to the same route, it works perfectly fine as shown in the browser's network tab. POST requests with a body like this one, work perfectly fine with a 200 return code:

data%5Bb2s_heartbeat%5D=b2s_listener&data%5Bclient%5D=b2s&interval=60&_nonce=0123456789&action=heartbeat&screen_id=blog2social_page_blog2social-calendar&has_focus=false

What do you think could be causing this issue?

Thanks for your assistance.

[Blog2Social Support]

Hello,

Thank you for your reply and thanks for describing your request.

This behavior seems to be unusual, and it would be awesome if you could send us a temporary guest account with admin rights for your WordPress website, if you would like us to check this case further.

We will, of course, treat your information as confidential. Rest assured, we will use this data for tests only.
You can delete the account as soon as our tests are complete.
Please be so kind as to include the login URL, login name and password of the WordPress environment if you are interested in this troubleshooting suggestion.

Please make sure to provide us with the requested files via a private message in the community in order to protect your privacy.

Thank you for your effort and understanding.
I am looking forward to your reply.

Best regards
Alexander