The gallery was not activated,
For use Pro version of OrdaSoft Joomla Gallery
Please check how activate of OrdaSoft Joomla image gallery
when I open a gallery page, it loads for ever without showing anything
How you create gallery on your site ?
You do this with help Menu or with help insert Gallery Short code to Joomla article ?
Please in joomla admin menu: System->"global configuration""->Server: "Error Reporting" - turn to "Development",
May be you will see some errors or notice ?
If this not help, for debug where error we must see your site at WEB
P.S. Please do site backup 2 times per month