Please have a look at your server's error log.
Please test this on several albums in your gallery and report your results.
Sorry it's taken me this long to reply back with my results. First, I tried this with several of my other albums ranging from 28-230 pics...all worked fine. Unfortunately, I wasn't able to view the error logs on my hosts server, however, the response I was given made since, especially when I realized the albums that works had pic sizes no bigger than 200kb and the pics I was trying to download into a zip file was between 1700 - 2000kb. Aparently, as quoted by my webhosting site:
"The issue seem to be that you site is timing out before the zip action
can be executed. What you are trying to do is very resource intensive.
Here is an example of the errors that are being generated.
[Tue Sep 22 08:59:48 2015] [error] [client 188.8.131.52] Premature end
of script headers: index.php, referer: htt"
They increased the memory and time for php to allow more time for the script to execute but it's still too intensive for a shared server. Right now, I'm doing further test and at the moment, 200 pic album with the pic sizes between the 1700-2000kb I mentioned about is working. I have about 1600 pics to upload so I'm creating several albums and will increase each one by 50 pics until I get to where it times out and gives me the error again.
Hope this helps anyone else who maybe experiencing this same issue. My hosting site does have other payment plans that might work so I'll be looking at those but in the meantime, this is where I'm at.
Andrea, I know I have other issues I've posted and I'll be getting to those as I can but this one was more of a major issue I needed to get addressed. Thanks for your help...