I have the same issue.
I am building a subdomain multisite.
I have the following plugins
Akismet
Amazon Web Services
Hello Dolly
Jetpack
NextGEN Gallery
NextGEN Pro
UpdraftPlus
WooCommerce
Wordfence Security
WP Offload S3 Lite
WP Super Cache
WP Updates Notifier
Yoast SEO
I have tried changing themes & permalinks and re-installing Jetpack.
Rookie question: Is JSON something I need to install? I hand crafted an AWS EC2 with CentOS 7 and installed Apache, PHP, MariaDB and PHPmyAdmin.
SELINUX maybe? I only asked because it kept PHP from attaching to a remote RDS MariaDB (which drove me nuts for a week).
