I just hit the same issue. justinj’s post saved me!
I had copied my 32GB max2play sd-card onto a new 64GB sd-card using Win32DiskImager under Windows 10 by „reading“ it to my local disk and then „writing“ the „img“ file to the new SD card. After that max2play booted up using the larger sd-card, but hadn’t expanded its filesystem. The expand filesystem button said it was already expanded.
So I searched the web, and was about to give up when I found justinj’s post.
So I deleted the mmcblk0p3 partition and rebooted, and the Expand Filesystem command now completed successfully on my new 64GB sd-card.
After another reboot I saw that the mmcblk0p3 partition had been recreated after the expanded root partition. So I need to remember to do this again if I ever move my max2play image onto another bigger sd-card .
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