"The plugin does not have a valid header."

I just found that this is a plugin clash. When I dosabled and deleted FooBox Free Image Lightbox then Media Library Assistant activated fine.

Thank you for your report and for your detective work in tracking down the conflict.

I found FooBox Image Lightbox (v1.0.14) in the WordPress Repository; is that the plugin you referred to?

I will have a look and see if I can resolve the problem. Thanks for your interest in MLA.

I have done some testing and discovered that this issue is an MLA defect, not anything to do with FooBox Image Lightbox (which has its own problems in WordPress 4.6 due to a known WordPress issue).

In my latest MLA version I changed the way example plugins are stored and accessed, and this causes a problem for new MLA installs. The “Activate Plugin” link on the “Installing Plugin” screen tries to activate an example plugin, not MLA itself. This fails because the example plugin isn’t installed. The defect occurs in WP 4.5.x and WP 4.6; I believe earlier WP versions have the same behavior.

Even though the install “fails” MLA is loaded in the plugin directory and can be activated from there without further problems.

I will work on a fix. Thank you for reporting this issue!

I have released MLA version 2.33, which corrects the problem you identified and reported. Thanks again for alerting me to the MLA defect.

I am marking this topic resolved, but please update it if you have any problems or further questions regarding the new release. Thanks for your help and your interest in the plugin.