I followed along with
https://wordpress.org/support/topic/nextgen-galleries-not-uploading-to-pages-since-update/
and tried all options listed, including deactivating all plugins and setting to the default theme.
No success.
Well I confirmed that I’m using your plugin, and only ever had yours installed, but was following the instructions for the woocommerce version.
I guess the functionality I was looking for was from another plugin, thank you for your time.
I did update the theme yesterday and had several errors similar to rschamess, but not the same. I found that the update removed several of the inc files, but I still had them on my local server. Once I uploaded the missing file, all was well again.