Looker shows Analytics data as "not set" when data is correct in GA

[Broonsbane]

Bit of an odd issue here... If I check a data set in GA4 (a table showing page views) everything looks fine, but if I create a table in Looker using that same data a large part of the homepage traffic is shown as (not set). If I add up the homepage traffic and the (not set) the total is what appears as homepage traffic in GA. Any advice is much appreciated!