Unfortunately, the link you provided returns an error 404 (file not found) so I'm currently unable to take a look at the problem live on your website.
Assuming that everything is set up OK on Fotomoto's own website, then if you are using WP-Juicebox (the Juicebox plugin for WordPress), all you need to do is:
(1) Upgrade the plugin from Juicebox-Lite to Juicebox-Pro following the 'Upgrading to Juicebox-Pro' instructions here.
(2) Enter fotomotoStoreId="0123456789abcdef0123456789abcdef01234567" (using your own Fotomoto Store Id) into the 'Pro Options' text area of the gallery settings window.
If you are not using WP-Juicebox, then just ensure that you set your fotomotoStoreId as a Pro configuration option in your gallery (for example in JuiceboxBuilder-Pro's 'Customize -> Sharing' section).
Either way, there is no need to use the Fotomoto plugin for WordPress. (It does not work in conjunction with WP-Juicebox and is not required at all for the Fotomoto functionality built-in to Juicebox-Pro.)
I hope this helps.
However, if you continue to experience difficulties, please post back with a working link to your gallery's web page and I'll take a look at the problem and hopefully be able to help further.
Thank you.
Edit:
I've just found your gallery (at 'art-work').
Your fotomotoStoreId configuration option is set correctly in your gallery (although I do not know if the actual store id is correct).
Please check that the id is correct and that you have the correct domain name set up in your Fotomoto account. These are the most likely factors to be causing your problem.
(Also, it is not necessary to have the Fotomoto plugin installed for Fotomoto functionality within Juicebox-Pro so you should be able to safely uninstall it unless you are using it elsewhere within your WordPress site.)