A Sometimes ibisPaint can't access "Photos" app due to "Privacy Settings".
Please change "Privacy Settings" by following steps below.

[Steps to change "Privacy Settings"]

1. Please open "Settings" app.
2. Please choose "Privacy", and then "Photos". You'll see list of apps that have requested to access "Photos" app.
3. Please verify if "ibisPaint" or "ibisPaint X" is set on.
4. If both of two are set off, please set on one of both.