Update :
Adding more context. This site went through migration. So i guess during the migration, something is happening that leading to this issue. Also once you done the steps below, you need to delete the plugin and install/activate again. That should resolve the issue.
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I was struggling with Jetpack to connect with WordPress. When you check, there is no significant error until I activate my Query Monitor and I start to notice connection to Jetpack API causing issues.
This was my first time so took me awhile to resolve.
Apparently it has something to do with HTTP/HTTPS and some certs. Eventually this particular web is a subdomain.
I am not sure the issue is due to that but after redeploy SSL certificate with HSTS & Server Side Redirection and as well as HSTS Preload, that seems to fix it.
Well I guess, if you are having no luck with connection issues even though you have disabled all plugin for troubleshooting purposes, maybe look at this option.
