I saw this error a few times after upgrading from ACF v3 to v4. The previous version of the plugin had the repeater field built in, and it was activated by entering a purchase key… but now (in v4) the repeater field is a separate plugin, downloaded from the store on this site. Other custom fields may behave the same way, like the Options page or the Gallery field.
You could try to roll back to ACF v3 and see if that fixes your fields – alternatively, purchase and/or download the repeater field from the store and install on your site.
As a disclaimer, the only reason I mention the repeater field is that your error of
invalid argument supplied for foreach() indicates that your site is expecting to loop over an object or array that doesn’t exist, and the repeater field is commonly used in this kind of implementation. I’m not actually sure if you are indeed missing the repeater field, specifically.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users
Helping others is a great way to earn karma, gain badges and help ACF development!