Check your permissions and clear your cache by turning on dev mode and then refreshing your site then turn dev mode off.

 
The following folders must have 777 permissions set recursively:
ow_pluginfiles
ow_userfiles
ow_static

Also this sub folder needs 777 recursively as well.
ow_smarty/template_c

If the problem persists let us know please. 

Recursive means that every folder and every file in the directory must be 777 

And then the sub folder of ow_smarty/template_c needs to be 777 recursive as well. 

Then take a look here to refresh your oxwall cache.  

https://wiki.oxwall.com/plugin-tuts:enable-debug

then just press control - f5 to fresh the page  then turn dev mode off. 

or you can get the free plugin called extreme cache in the store that will clear your cache for you without editing the config file. 

hope that helps

Thanks for your help