I have a license key for ACF PRO, which I acquired last week. I have successfully updated to version 5.1.4 on one development site, but the second refuses to allow me to update.
Essentially what happens is that i enter the license key, the banner comes up that declares it to be activated, and when I move to the plugin update page, it has not actually activated. Then, when I revisit the ACF updates page, it is as if I had never entered the license key at all. I have made two successful updates out of three, my account states 3 successful activations, but only two actually updated.
There happened to be a weird bug in this WP development installation (3.8.1), in which the Visual Editor tab was not working (only the text Editor tab worked), and I wondered if that might be a related issue. I have asked the dev server support to look into the editor issue, but I thought that perhaps someone might have experienced something similar, and could offer ideas about how to resolve it, if that is possible.