This is a curious problem, and I hope someone here might be able to shed some light on it.
I have a test site on my laptop that I use to make sure everything is set up and configured the way I want it, then I duplicate those settings on my live site. Unfortunately the test and local site aren't 100% duplicates (the live site uses a different flavor of Linux, and so I can only approximate the environment). But for a very long time the only tweaks I had to make were back-end things -- settings in apache, caching, etc.
However, I recently switched to Fedora on my laptop (live site is Ubuntu) and ever since then I haven't been able to display anything on my test site that uses the Panels plugin. I've verified that it is Panels, and nothing else. If a block or a view is displayed outside a panel, it's fine. If it's inside the panel, however, it disappears completely.
It displays perfectly well on my live site (Ubuntu), but not on my test site (Fedora, running on localhost). Both sites are running the same theme, and my test site uses backups of my live site database, so it's the same data.
Does anyone know why that might be? It's confounding, and it makes me nervous, since I now have no way to test some rather significant parts of my site...
Comments
Check the file permissions
Check the file permissions and ownership on the panels module folder and files.
Contact me to contract me for D7 -> D10/11 migrations.
Just checked...
... they have the same file permissions and ownership settings as the modules that work.
Edited to add that I can access panels from the admin section -- I can create them, add content to them, and modify content in existing panels. But I can't preview them (I get blank results) and when I try to display them they display as empty html tags.