API connect - We found extra characters at the end of JSON input

Hello,

I have a problem, I get an error:

DataFormat.Error: We found extra characters at the end of JSON input.

Details:

Value=

Position=0

and this is about action =Json.Dcoument(GetJson)

Here my code:

let
 authKey ="Basic " & AconexAuthorizationPair, //100% works

//Retrieve token from Aconex
GetJson =
 Web.Contents(
 "https://eu1.aconex.com/api/projects/XXXXXXXXXX/register",
 [
 Headers=[
 #"Accept"="application/xml",
 #"X-Application-Key"=AconexIntegrationID,
 #"Authorization"=authKey
 ],
 Query=[
 #"search_query"="doctype:Plan",
 #"return_fields"="trackingid,title,doctype,docno,attribute1,forreview,filename,fileType,fileSize"]
 ]
),

FromatAsJson = Json.Document(GetJson),

//Extract token from Json response
AccessToken = FromatAsJson[access_token]

in
 AccessToken

 

of course above in Power Automate I just provide normal username and password, with PowerBI it is in a Base64 format username:password - but this works.

 

I think there is no token exchange, I have this code as I found it somewhere in connections with OAuth2 for Spotify, here I just need a plain JSON response, I think problem is caused after Web.Contents -> and this is a place where I don't knwo what to do.

 

Any help would be appreciated.