In the composer I can launch to External Image Editor (photoshop) and when I do something simple like draw with a brush or adjust Hue/Saturation, when I press Command S it saves automatically and the changes are immediately seen in CTA3. HOWEVER, if I try to do anything more complex, like draw a mask or even insert a shape, when I press Command S it brings me to the save screen and when I save nothing happens in CTA. Please help. Thanks so much!

When  you create layers or masks, Photoshop wants to save as the default Photoshop format. Make sure when you are creating your image its saving the file in the original format, not creating a different file with the same name in a different format. So do a (save as) instead of just save. this way you can see the format its trying to save in. ( another indicator is you should always get the (Are you shore you want to overwrite message when you save). 

I'll try to be a bit more clear now that I have been awake a few hours. Image formats like JPG, TIFF and others don't have information like masks or layers. So when you add information outside of the format the original file. Photoshop doesn't want you to loose this information so it default to a PSD file format to save all this layer and mask  information. So by doing the "save as" you can save it in the format the original file is. The great thing is Photoshop will do this converting in it's head so to speak  while leaving your project where you were and allowing you to keep changing it. 

I will sometime keep my PSD version to, because I might want to edit later or over time. like creating a clothing material then later add a stain or damage over time as shooting. By keeping the PSD version I can return to the layer version and just continue or go back to a previous version. If you flatten or just save the Image file your stuck in the present state and have to edit this version or start over.

In the composer I can launch to External Image Editor (photoshop) and when I do something simple like draw with a brush or adjust Hue/Saturation, when I press Command S it saves automatically and the changes are immediately seen in CTA3. HOWEVER, if I try to do anything more complex, like draw a mask or even insert a shape, when I press Command S it brings me to the save screen and when I save nothing happens in CTA. Please help. Thanks so much!

Hi and thanks of the response. I'm editing one of the template characters so I followed your advice and saved the file as a PNG but the same issue is occurring- it's not updating in CTA. Perhaps I'm saving it into the wrong folder? I'm saving it into the CTA3 temp folder, which is where it already is. 

I've tried flattening the image as a workaround. It updates in CTA but adds a box instead of being transparent. Do you have any other thoughts? I'd really appreciate it! 

I tried saving it as .png same result. Do you have any other suggestions? I really appreciate it! 

make sure you are writing back over the file iclone exported. into the temp folder. I'm thinking it's a JPG. I mentioned PNG's as well but for type reference. After you export the file and then edit do save as and look at the file and make sure what it's extention is, and match it.

Just to add to what Paul said, when you send something to an external image editor you need to just press save and not anything else because it sends the image to a temp folder which CTA updates from. If you are adding layers in photoshop you need to merge all layers into one, before you can just press save to send the data back to where it needs to go.

Thanks everyone for all your help. I figured it out at the end. When I change the file type to PNG it added the word copy to the file name. Erasing the word copy and saving it into the Temp folder worked. Hooray!