Moved to Knownhost… now problems popping up

I ran into several problems with the “write to header” issue but found a workaround for that but one HUGE problem remains, as it deals with 90% of my content.

I use the Picbox plug-in but after the site transition, where the gallery would be normally displayed, it now shows “Missing attachment” in its place. No code error or anything so I’m lost where to start looking.

I’m in desperate need of help here. My site is basically useless without this plug-in working.