If you see the Juicebox logo in the lower right corner of your gallery, then your gallery is indeed Juicebox-Lite instead of Juicebox-Pro. (This branding is not present in Juicebox-Pro galleries.)
All you need to do to upgrade the gallery from Lite to Pro is replace the gallery's Lite 'jbcore' folder with the Pro 'jbcore' folder from the Juicebox-Pro v1.5.1 download zip package ('juicebox_pro_1.5.1/web/jbcore/').
Alternatively you can open and re-save your gallery in JuiceboxBuilder-Pro (and then re-upload the gallery to your web server, ensuring that existing files are overwritten).
Instructions for upgrading a gallery from Lite to Pro can be found here.
If your gallery still seems to be Lite, then try clearing your browser's cache to make sure that your browser is using the latest files from your web server (instead of older cached versions).
I hope this helps.
However, if you continue to experience difficulties, then please post back with the URL to your gallery so that I can take a look at the problem for myself and hopefully help further.
Thank you.