When I try to upload a zipfile (zipped series of images, not a folder of images) with K2 joomla responds with "Item saved", but I can't see any images in the k2 article (frontend nor backend) and when I look at media/k2/galleries or images/stories there are no images. Permissions on these folders and on the cache folder are 777. What could be going wrong?

Thanks for spending your time on this
Eric

Check the permissions of the temp folder. The zip file is primarily uploaded there and then moved to media folder.

Which temp folder do you mean? The /tmp in the joomla root? I made both a /temp and a /tmp folder in  /images/stories, just to be sure. All these folders are 777. Did I miss a folder?

You missed media folder. K2 stores all images, galleries, etc in media/k2 folder.

I have a website which use Simple Image Gallery Pro, that was transferred (by the provider) from "/home/***/domains/***.nikkelhost.com/public_html" (*** is my account name with the provider, nikkelhost.com is the provider) to "/home/***/domains/www.studioaai.be/public_html" on the host server. Before it got transferred, SIG-pro used to work fine, after the transfer the problem started.
Is there another temp folder?

Check your permissions please.

Check your permissions please.

I did check my permissions on every image and media folder, subfolder and temp or tmp folder I can think of, setting all of them to 777 does not help, that's why I'm asking: did I miss a folder?

You missed media folder. K2 stores all images, galleries, etc in media/k2 folder.

I checked this (time and time again), media folder is 777, media/k2 is 777 and all media/k2 subfolders are 777.
Do I need to create a tmp folder in media/k2? Because there isn't such a folder in it...

Do other plugin files like plugins/content/jw_sigpro.php etc need specific permissions?

It's really puzzling me, any help is very much appreciated...

Pm me access to your super admin please.

I've upgraded k2 to 2.4.1 but the problem remains...