Why some wordpress themes not behave as they are in demo while all images, css, and plugins files are at same location. and some themes behave differently if use to another server. two examples are http://wpjunction.com/themes/classicmag/ and http://wpjunction.com/themes/quench/
What server it's one doesn't have anything to do with it, unless there are specific Funtions that you server doesn't allow, that are in the original theme...such as SMS messaging. There are a lot of reasons that you might see a discrepancy. A lot of third party sites are hosting theme files. It could be that what is shown is not the same as what is on the download link...maybe the theme author upgraded, but hwo ever is displaying the theme hasn't. Maybe the original has plug ins working that were not mentioned. The theme may be deomo'ed on an older version of WP, and not compatible with our current version. The theme could be coded poorly,(not the same on all browsers) as is the change you take on free themes. There are a lot of reasons.
I always check these things and download only from designer site new version. try these two plugins or classic mag and u will see what i am saying
There is really no way to say as each theme has it's own issues depending on who designed it, and for what use. Unfortunately, when you are dealing with free themes from unknown coders, you sometimes have to "kiss a few frogs". Some designers are better than others. What specifically are you having a problem with ? what theme ?
For designdesease, flickr plugin installed perfectly, but i can not see flickr img. ( settings are same for other working themes) For deluxe themes i upload theme without any editing and at one server i see panel for theme settings but for another i did not find any theme panel For Woothemes, which are really cool, freshnews theme i can not fix featured tabs, featured posts just destroying the theme.
It's almost always a configuration issue. Many designers do not write the best tutorials on setting up their themes. They usually know so much about them that they overlook what the average guy might find confusing. Their support forums can be helpful ... but not always. When you purchase a theme they will usually support those themes. I try to figure everything out on my own first, then compile my list of questions. After a little back and forth I've always been able to get everything working properly. Sometimes themes are dependent on plugins being installed, configured, and of course activated before they function properly. This creates potential issues down the road as themes are not always updated to coincide with plugins. But that's how things are... and this is true of all software over time.