neophyte question, sorry for that : I cannot find the "ndxz_users" table in "files" or anywhere else, as the "Admin button" disappeared when resetting password..
In case anyone is interested, for some strange reason, after updating to 2.1.4, the column "user_admin" in the "ndxz_users" table was set to 0 instead of 1, so the is_admin() check was returning false and thus disallowing the access of many of the Admin tabs and hiding the Admin link itself.
So, to fix this:
1) Access your database via phpMyAdmin or a similar tool in your hosting.
2) Go to the "ndxz_users" table (your table might have a different prefix instead of "ndxz_")
3) Change the "user_admin" column of your user from 0 to 1.
Now, the Admin link should appear again.