Web.content error when combining queries

It's because you are using a variable as a URL. If these are all google sheet then i assume they all have the base URL of: https://docs.google.com/

you can try removing this from the URL first.

URLPre = Table.ReplaceValue(BRON,"https://docs.google.com/","",Replacer.ReplaceText,{"Column2"})

In web.contents you just the url as  "https://docs.google.com/". Then you append the rest using RelativePath

SourceAccessKey = Xml.Tables(Web.Contents("https://docs.google.com/", [RelativePath = URLAuth, Query=[accessKey=Text.From(AccessKeyParam)]]))

  let
Bron = Csv.Document(Web.Contents("****GoogleSheetLink****"),[Delimiter=",", Columns=4, Encoding=1252, QuoteStyle=QuoteStyle.None]),

URLPre = Table.ReplaceValue(BRON,"https://docs.google.com/","",Replacer.ReplaceText,{"Column2"})

URLAuth = URLPre{1}[Column2],
AccessKeyParam = AccessKey,
SourceAccessKey = Xml.Tables(Web.Contents(URLAuth, [RelativePath = "https://docs.google.com/", Query=[accessKey=Text.From(AccessKeyParam)]]))
  in
SourceAccessKey
	

In the service when you add to gateway, you can check "Skip connection test". This is checking if https://docs.google.com/ is a valid URRL. In this case it is, but for others reading this solution may not be.