I guess that you have old version of the gallery (some gallery version before 2.7.0) In few latest versions we have made some core modification in gallery functionality. One of the key modification related with cache of the gallery and optimization of the jquery library usage.
Some of the releases had problems with alternative JQuery modes. In the case if you had alternative version of the jQuery selected in gallery settings then it’s could work this way.
Please update your gallery to the latest version, then clear gallery cache or just open settings of the gallery ans save settings. After this action gallery re-generate cache of the gallery on the front end.
If you’ll have some other questions or problems related with our gallery plugin feel free to post your request here.
