Running pg_upgrade Version 11

Hello,

Trying to run pg_upgrade from version 10 to version 11 on the test
server and pulling the following error:-

could not open version file: /home/postgres/testing/data_v10/PG_VERSION
Failure, exiting

O/S is:- Debian 4.18.10-2 (2018-11-02) x86_64 GNU/Linux

Running pg_upgrade as user postgres.

These are the permissions on the version 10 file:-

-rw------- 1 postgres postgres 3 Mar 23 2018 PG_VERSION

These are the permissions on the version 11 file:-

-rw------- 1 postgres postgres 3 Nov 6 14:50 PG_VERSION

This is the command being run:-

/usr/lib/postgresql/11/bin/pg_upgrade -b /usr/lib/postgresql/10/bin -B
/usr/lib/postgresql/11/bin -d /home/postgres/testing/data_v10 -D
/home/postgres/testing/data_v11

Logged in as user postgres and postgres owns the files created by
initdb, so is this a permissions problem or am I having a brain fade?

TIA,
Rob