I converted Japanese to English with translation software.
I was able to load PNG sequences in my environment without any problems.
I can advise you if you explain in detail.
1) Is it possible to export a PNG sequence from Adobe Character Animator?
2) Is it a serial number?
Step1
Start Animate2021.
Step2
Create a "new" project. (Example: 1920 x 1080 24 fps)
Step3
Select "Load"-→ "Load to Stage" from the menu.
Step4
Select the file "Name.00.png" from the folder containing PNG.
Step5
"This file is part of the sequence. Select ~" → "Yes".
Step6
The sequence PNG is loaded into the timeline.
Although it is in Japanese, the commentary video has been uploaded to YouTube.
https://youtu.be/gL3zj-TAcbI
Thank you.