Our announcement for PP8 is on this site. I know we state to look over the included documentation with the downloaded code for complete instructions.
The installation instructions with PhotoPost 8 have the same stuff on vb4 you need to do as an upgrade. You need to generate and install the vb4 plugins.
Next issue is not a bug as we do not hard code it to anything persay look at how it is done
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The response I would give based on looking at our coding if that you would need to ensure that your forum url has been entered correctly in your PhotoPost Admin -> Forum Settings. If your forum url is correct the image should be found.