Actually, think I might see the problem. On ARCHER2 your .bash_profile is loading a really old version of our um environment and thus picking up cylc 7 instead.
On ARCHER2 in ~/.bash_profile
Change
. /work/y07/shared/umshared/bin/rose-um-env
to
. /work/y07/shared/umshared/bin/rose-um-env-puma2