Sounds like it is corrupt. Do you have a card reader so you can plug it into the computer to see if your computer sees it? If not, if you boot into recovery can you mount it usb and try to have computer see it?
If the computer sees it, I would reformat it. Gparted or Mini Partition Wizard work in windows.
Thanks
When I use miui version then not show in place of A2SD+.a massage show device not supported A2SD+.Is miui support external SD. Or need any other sitting for this.
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