Problem with uploading photos

[Andy96]

We have not had problems with our Gallery for a while but a few days ago we tried uploading photos and an error message comes up reading ... "Unable to create thumbnail or reduce size" we have followed the instructions that other users have used.
"Try to go to Config >> Files and Thumbnails Settings >> Max width or height of an intermediate picture/video and reset this from 1 to 400"
we check it and it was 400 already.. we also have another problem as we are new we are still unsure on who to solve it.

[phill104]

It probably means some file permissions have changed on your host. Check those are as per the docs and if that fails pease read the upload troubleshooting section and do everything outlined so we can help you further