Filtering Issue - GA4 & Looker data are different for the same filter

[Ben06]

Hi,

I have a filtering issue in Looker with GA4. I am trying to display my traffic by Source / Medium in order to show all the traffic coming from Search Engine Marketing channels.

Data in GA4

In the past 28 days, GA4 shows that I had 655 sessions coming from:

• google / cpc,
• bing / cpc
• adwords / ppc

Data in Looker

When I apply the same filter in Looker, I see only 80 sessions.

I do not undersand why for the same set of data, the same filtering, the results are completely different. 

Please note that when no filtering is applied in Looker, the data matches exactly those of GA4.

Thank you in advance for your help.