Same problem here! Came back from vacation and got the same error message like @SupperDad .
Linux nextcloudpi 4.19.57-v7+ #1244 SMP Thu Jul 4 18:45:25 BST 2019 armv7l GNU/Linux
Nextcloud version 16.0.2.1
@j-ed Which permissions should be set for config.php? These are mine: -rw-r-----
This thread seams to discuss the same problem: Nextcloud hangs on/stuck on : CAN_INSTALL file missing after upgrade
Regards
soe