Can't delete folders - Locked?

I am having some sync errors between my linux desktop client and with my Nextcloud Box on a RPi2, after deleting some files and folders on the laptop
I am managed to delete the offending files directly on the Box via Firefox.
However I get an error when trying to delete their folders on the box through Firefox
I searched and found that it could be because they are 'locked’
I cobbled together these instructions from various places:

Manually disable locking state:

  1. Put ownCloud in maintenance mode: edit /var/snap/nextcloud/current/nextcloud/config/config.php and change ‘maintenance’ => true,
  2. You can access the SQLite database in linux by installing the sqlite3 package.
  3. In the terminal, type sqlite3 /path/to/nextcloud.db
  4. Empty table oc_file_locks: run: DELETE FROM oc_file_locks WHERE 1;
  5. Disable maintenance mode (undo first step).

I managed steps 1 & 2 but cant find what the path to nextcloud.db is for snap

I thought it might be /var/snap/nextcloud/current/mysql but I dont have permission to enter there

I found this, but its not much help

I think it is there but I cant open it:

ubuntu@ubuntu-standard:~$ sudo sqlite3 /var/snap/nextcloud/current/nextcloud/mysql/nextcloud.db
SQLite version 3.11.0 2016-02-15 17:29:24
Enter ".help" for usage hints.
sqlite> DELETE FROM oc_file_locks WHERE 1;
Error: unable to open database "/var/snap/nextcloud/current/nextcloud/mysql/nextcloud.db": unable to open database file

Can anyone help me please?