Are all of the websites under the same hosting account? Are all of the websites on the same hosting servers? Our websites are all under 1 one hosting account, but our sites are on 3 different hosting servers. It could be a server-side issue if all of your websites are not on the same host or hosting servers. The BPS Pro upgrade check is made using the WordPress wp_remote_post() function that sends the request to our API server. If something like server-side caching is going on in your wp-admin backend area then that could affect the BPS Pro upgrade check. So things to check would be website caching, server-side caching and of course anything else that would interfere with the wp_remote_post() function.