GA4 data source in Power BI suddenly failing with DataFormat.Error (unexpected character in JSON)

Hi everyone,

I'm connecting to Google Analytics 4 (GA4) from Power BI Desktop, and this has been working without any issues until today. Starting today, every refresh/connection attempt fails with the same error, regardless of which property I try to connect to. I select the GA4 data source and proceed as usual, but I get:

 

DataFormat.Error: We found an unexpected character in the JSON input.
Details:
Value=<
Position=0

 

A few details about my situation:

- Nothing changed on my end, the same reports and connections worked perfectly until today.
- The error is identical no matter which property I select.
- I'm following the normal flow: choosing the GA4 data source and proceeding.

Since the unexpected character is `<` at position 0, it looks like the connector is receiving an HTML response (e.g. an error or sign-in page) instead of the expected JSON. I'm not sure whether this is something on the Google side, an authentication issue, or a problem with the connector itself.

Here is the M code I'm using:

 

let
    Kaynak = GoogleAnalytics.Accounts([Implementation="2.0"]),
    #"accounts/XXXXXX" = Kaynak{[Id="accounts/XXXXXX"]}[Data],
    #"properties/XXXXXX" = #"accounts/XXXXXX"{[Id="properties/XXXXXX"]}[Data],
    #"properties/1" = #"properties/XXXXXX"{[Id="properties/XXXXXX"]}[Data],
    #"Eklenen Öğeler" = Cube.Transform(#"properties/1",
        {
            {Cube.AddAndExpandDimensionColumn, "day", {"day"}, {"day"}},
            {Cube.AddAndExpandDimensionColumn, "month", {"month"}, {"month"}},
            {Cube.AddAndExpandDimensionColumn, "platform", {"platform"}, {"platform"}},
            {Cube.AddAndExpandDimensionColumn, "year", {"year"}, {"year"}},
            {Cube.AddMeasureColumn, "sessions", "sessions"}
        })
in
    #"Eklenen Öğeler"

 

Has anyone else started seeing this today? Any idea what's causing it or how to resolve it?

Things I can confirm / am happy to check:
- Power BI Desktop version: 2.155.756.0 64-bit (June 2026)
- Connector used: Google Analytics (GA4), Implementation 2.0
- Authentication: signed in with my Google account

 

Any help would be greatly appreciated. Thanks!