I'm creating a new post, then use the attachments tab, I upload a very small .jpg or .png file (10kb, 40x40), the image line appears but the "Place inline" button stays hidden.
When I'm trying to do the same in a post that already contains images, I get the same behavior, but the lines with the previous images do contain the "Place inline" button.
This phpBB forum is the production one, and I have an exact copy in a QA forum with the same user, the same permissions, the same settings about the allowed sizes, php.ini settings, and so on.
The account I'm using has the admin perms. I also tested it with a basic account, to no avail.
Though, some of my users are using it with no issue.
This is driving me mad because I find no difference between the QA and the prod instances.
I think I finally found what caused this issue : config[attachment_quota]
The difference between my prod setup and my WA setup was that my prod setup already had a full bunch of images lying in the files dir, when my QA files dir was almost empty.
So, it was just a quota matter.
Too bad no error msg nor warning arose neither in the web gui nor in the inner logs to understand what was going on.