[Plugin: NextGEN Gallery] 404 page on image path!!!!

Hi there!
first af all thanks for this plugin, it’s years I used ??

in one of my main website I got a this problem:
I upgraded from wpmu to the current version of wp (multisite)
than I activae the plugin and install the upgrate.

Now I can’t see any of my galleries!
even if the gallery exists I get a 404 not found page on the image path
(I checked on via FTP)
example https://travellertribe.com/graz/photo/

please it’s really important to me to solve this issue

https://www.ads-software.com/extend/plugins/nextgen-gallery/