I installed Zenphoto a couple weeks ago and have been playing with it and it was working fine. Then a couple days ago I got a error message saying the setup files not found.

I re-installed again yesterday and it's working fine so far.

Question: what caused this error? and wondering if it will happen again?

Running version 1.4.2.4 installed via Softaculous.

Please see http://www.zenphoto.org/news/installation-and-upgrading#re-running-and-re-uploading-setup-files

Thank you, I'll read the post.

Also note that very often we have this sort of problem when third party installers are used. We really do not know what these installers are doing, but unless they use intact the Zenphoto installation routine they are prone to subtile errors downstream.

As to what caused the error, it is a "who knows" situation until the 1.4.3 release where the message will tell you why.