Krikor wrote: @Javier, was GD not installed in the first place, or was it outdated?

Before the update, GD was not installed on our server

Just out of curiosity, when you resized images (K2 Images) didn't you get fatal errors?

Its the "old problem" - since a few days/weeks I cannot upload any images in K2. If I try to choose an image which is already on the server only a blank window opens. If I try to upload it, the opening page is empty - an the image is not online. I can upload (an image) as an attachment - but it doenst help me to show it in the article. Any solutions? I tried evrything in this thread... nothing solved it.

Versions:
Joomla 3.8.13
K2 2.9 (it already didnt work in 2.66)
PHP 7.0, 5.6,.... I tried different, but it didnt help.

www.mennoniten-hh.de

Maybe it helps someone. I had this problem too. I changed folder rights of:

/media/k2/items/

to 775 instead of 755 and it fixed the problem !