We've had reports from users on Android seeing an error message "File format or size is not supported yet".
When people see this message it is usually because they are working with a very large canvas, and/or are running out of space or RAM on their device.
It may have been triggered when you added an image to a canvas, or opened a canvas from the Sketchbook Gallery.
First thing to check would be the size of your canvas - sometimes people end up creating very large canvases with many layers, which end up being huge files for a mobile device to handle. If you have lots of layers, see if you have any you don't need and can remove. Also, see how much storage is available on your device, if you are low on storage it may not be possible to create or open an image file.
If you are working with a large file, try to free up some RAM - a shutdown/restart of the device is one way to free up background processes you didn't know were still running, or just make sure you aren't running multiple apps at the same time.
Finally, we have heard from some users that they see this message when importing an image from their Downloads folder, or sometimes from Google Drive. If this might be the case for you, try moving the image you want to import into your Documents folder.