Thanks for reaching out to the Roku Community!
We'd like to take a closer look to see if there's anything else we can suggest to help. What was the error message when attempting to upload photos?
Please be aware that a stream may not allow 100 photos if the storage limit for the Roku account has been exceeded.
Here's a link to our support page to find out more about the feature: How to use Photo Streams on your Roku® streaming device | Roku
Keep us posted and we'll continue assisting from there if needed.