@Alexander Gowan - I am not graphics expert, so bear with me. 

The attached PNG is a file I found from a Google search and it does appear as “transparent” in a Miro board:

To learn more about the file you are experiencing issues with, if it isn’t confidential, you could put the PNG into a Miro board and share a link to the board here? If you have a paid plan, you may be able to use Anyone with the link → Can view. You may need to adjust the Board Content Settings to allow for it to be downloaded.

Thanks for the quick response!  The cat image works, but the PNG below (stock from msft) is transparent in PPT but white background in Miro???

@Alexander Gowan - I found the slide in PowerPoint with the stock image you included and it appears that the woman is not a transparent PNG, but the man is (for me at least). I have attached the PNG files I downloaded from the slide:

And when I move them around in the slide I see that the are not both transparent:

Thanks!  I also found that copy/pasting PNG images is not consistent.  Uploading is the better way to retain formatting.

Thanks again!