Are you able to check your PHP error logs and report on error messages from there? Often times, the spinning wheel will point to an error that might be occurring on your site.
As far as I can check the error logs, there are no fatal errors reported, only plugin exception logs are generated. If I inspect through dev tools it displays the citation URL.
It is my understanding that all AddThis services, including the AddThis plugin, was terminated in May 2023. AddThis is/was owned by Oracle who made the business decision of getting rid of the service. A press statement of this decision can be found here: https://www.addthis.com/. Our institution has been testing the Shariff plugin as an alternative, as many of our journals rely heavily on using the social media buttons feature in OJS as a way of easily sharing articles. It may be worth looking into the Shariff plugin as an alternative. It supports a much larger group of social media platforms beyond the standard big ones (Facebook, for example), to include LinkedIn, Reddit, and many more. I hope this helps!