I did find a work around that gave me the size I was after. I opened the image that was undersized and edited the image size. I then hit save and it finally saved in the correct 18x24 size. I will try the other process again to see if it does it. I have a few pictures that need resized in three different sizes.
Sorry to hear that you ran into this limit. We do in fact have a limit right now on the exported image.This is a maximum number of total pixels for an exported image, not specific dimension sizes. For now on a 64bit machine you can have images up to 100MB (for example an image 10k x 10k) and up to 25mb on a 32bit machine. The size limit is for the size of the exported image, not the PSD, so you can have a large PSD as long as you are only extracting smaller layer. This also applies to scaling, so even if you have a smaller image but scale it up 1000% then you might also hit that limit. We should be addressing the limits in an update to Export.
Any sign of when we might see an increase in this limit in CC2017?
A new Banner 36" by 72" at 300dpi (10,800x21600) maxes out Exporting at 65% scale image, or 7020x14040, which at 98,560,800 total pixels sounds like this August 2015 limit is STILL here in 2017 or am I, hopefully, missing something else that might be capping me to this image size?