Have you tried updating WP to 4.3? There have been changes in ACF that where needed to work with WP 4.3 that may have something to do with it.
If this doesn’t work then you need to try deactivating other plugins and switching to a default theme. I have a site with WP 4.3 and ACF 5.3.0 and everything is working, but ACF is the only plugin installed.
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