Is your device a T8-S (if so, are you able to access the card in openELEC (it'll likely be under /var/media/ if you're in Kodi's filemanager)?
If you've a T8, or T8-S and openELEC can't see it either (switch back to Android now please), if you head to Settings (two cogs on the launcher's homescreen) then (first backup all data from the SD card you might need):
OTHER tab
MORE SETTINGS button
STORAGE entry
Scroll down the right hand side of the screen
Can you see your SD card listed there, under "SD CARD"?
If it shows Mount SD Card in greyed out text, skip to the next paragraph.
If the Mount SD Card is present but not greyed out, click it. Check whether you can access the SD card now.
Return to the launcher's homescreen and click the circle with six dots. Now click on the ES File Explorer shortcut
Cancel the update request (but do sometime sign into the Play Store if you haven't already -
https://droidbox.co.uk/blog/faq-2/googles-play-store-signing-in-and-auto-updates/ ) and close the intro screens by clicking OK.
Expand the LOCAL menu on the left, and check if the SD card is listed there, and if so, what happens when you click on it.
If still no joy, take the card, plug it into a PC/Mac and reformat the card (FAT/FAT32 only please, at least for Android)
more to come, posting then adding screen shots:
T8-S with SD card inserted - Storage screenshot
T8-S with no SD card inserted, same area
ES File Explorer (white skin from app update) with SD card inserted (
sdcard1 at the bottom is the SD Card, 0 is internal storage, sda1 is my SSD drive inside the T8-S and sdb1 is a USB thumbdrive):
Same system and app, no SD card ( sdcard1 )
I've included the screens so we've got a common comparison point to start from.
Hopefully the final step of formatting the card (I'd turn off Quick Format if offered) will be enough.
If that doesn't help, see if a different card (or even microSD card if you still have a physical adapter) helps, or possibly run chkdsk on the original card (or Mac equivalent).