Double-check what your thin client motherboard is compatible with. Your post title says mSATA, but you linked to a M.2 that you bought, they’re a bit different and are not interchangable AFAIK.
e.g. maybe this helps https://www.kingston.com/en/blog/pc-performance/ssd-form-factors
In any case the BIOS should show that something is plugged in once you have it plugged in correctly.
Was going to comment the same, this issue has existed for some time for other apps. LibreTorrent ran into the same issue and now the F-Droid version is their full-featured app while the Google Play version is restricted due to Google.
Interesting that Nextcloud managed to last this long on Google Play without running into the same limitations (until now that is).