This is a very specific problem so it might only work for some. After I updated WordPress and all plugins on an old site that used WordPress Custom Fields to enter some data, the Custom Fields in admin disappeared. I could add a new post but Custom Fields were nowhere to be sen, not even in the screen options.
Long story short, after doing some searching on the net, I found out it was ACF (Advanced Custom Fields) fault. In new version of the plugin they disable WordPress Custom Fields because they think you are using ACF anyway so no need for both. Not sure I agree but here is 2 ways you can try to solve it:
- If you activated ACF but are not using the plugin, just disable it. WordPress Custom Fields should come back.
- If you want to keep both then add this code to your theme’s function.php file (the best is the child theme, if you have one)
WordPress Custom Fields should reappear now.