I trust this helps others.

Sorry, no. Grepping the complete original source I can't find any line referencing OSSNuser.
Thus, using this var or not shouldn't make a difference.

Glad that you resolved it!

I unthinkingly set a cookie called OSSNuser. This caused the issue and calling it something else solved it.

I trust this helps others.

If it exists in the folder but not displaying then there is error with your website maybe you have modified something which is causing the issue.

It has uploaded, since it exists in the ossn_data/user/1/photos. It is those file names referenced by the link in the HTML (https://prod.localapp.live/album/getcover/175/de2b2eafaaea28d53c21287b8f0d6a60.jpg?ossn_cache=1d2c3f74), but they are not displayed when you use that link in another tab.

To my mind, it is strange that it refers to covers.

If I add an image using the camera icon, again it is not displayed, e.g. https://prod.localapp.live/comment/staticimage?image=c2lmUGhEeDJrTHU0ZkZzd3E3S3BpSHRwcVhjVWdPajFjaEt3endYTS9HMEUzOWVZRjdJTjBRQmx4WGltNjNSbg==

If it is not there that means its failed to upload, like last time you had issues with writing permission. Try to upload under 100KB photo if it fails that means you have issues with the upload if they upload then you need to increase memory limit , upload size and post max size.

I see you may have already created a couple of posts, whose photos are not appearing. (guids:19 and 20) The photos are not appearing under objects in the data directory either.

This is how it looks like! which thumbnail photos do you mean not loading?

Apologies. If you visit https://prod.localapp.live, you will find that thumbnail photos do not appear.

I believe you had login details previously for LocalApp. These would be current now.

It would be most appreciated if you let us know what exactly you wanted to achieve .