Before proceeding further, can you please try the following?
1) Take a full backup of your site and database before proceeding.
2) Update WordPress to the latest version.
3) Deactivate all plugins except WPML.
4) Switch to a standard theme like 2024.
5) Try again connecting your sites and check for the issue if it still happens.
Please let me know and I'll try my best to help you further on the matter.
I had this same issue with my production site coder.hocl.dk was migrated with hocl.dk
I contacted support and they wanted access to the site and fixed it. I didn't need to update anything. So, I think the update has nothing to do with this. the site was updated a few days ago.
So, if you want the access I can provide it for you.
I need to take a closer look at your site. So I request temporary access (WP-Admin and FTP), preferably to a test site where the problem has been replicated.
Your next answer will be private, to share this information safely.
Also provide detailed steps to reproduce the issue and links to pages in the admin and on the frontend.
IMPORTANT: Please take a complete backup of the site to avoid data loss. I may need to activate/deactivate plugins also.
I need to take a closer look at your site. So I request temporary access (WP-Admin and FTP), preferably to a test site where the problem has been replicated.
Your next answer will be private, to share this information safely.
Also provide detailed steps to reproduce the issue and links to pages in the admin and on the frontend.
IMPORTANT: Please take a complete backup of the site to avoid data loss. I may need to activate/deactivate plugins also.