Thank you for using ibisPaint.
Our app has a function to browse the official site (ibispaint.com) on the screen that is opened by tapping "Online Gallery" button.
You can comment to artworks on Online Gallery or download artworks to your "Collection" if you log in to ibispaint.com at this screen.
However, after October 5th, 2021, due to changes in the specifications on Facebook side, Android version app may not be log in with Facebook account in "Online Gallery" and these functions may be unavailable.

We are currently preparing a countermeasure for this issue.
We apologize for any inconvenience caused to users of Android app who have logged in to Online Gallery using your Facebook account.
Please wait until the countermeasures are completed.

You can still use your Twitter / Apple account to log in to Online Gallery and download artworks until we've completed countermeasures.
Also, even after October 5th, 2021, you can log in to https://ibispaint.com with your Facebook account using a browser app such as Google Chrome, so you can comment to artworks. (Downloading artworks to "Collection" is not available by this way.)
Note that downloading brushes from "Online" button in the Brush window is not affected by this issue because it is no need to log in.