Error - 'Can't save dataflow. One or more tables references a dynamic data source'

Hello all,

I have an issue transferring some M from desktop (where it works fine) to run in the service.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjIwMlCK1QEzDGEMIxjDGMYwUYqNBQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Year = _t]),
    #"Added Custom" = Table.AddColumn(Source, "Custom", each Json.Document(Web.Contents("https://date.nager.at/api/v3/publicholidays/" & [Year] & "/GB"))),
    #"Expanded Custom" = Table.ExpandListColumn(#"Added Custom", "Custom"),
    #"Expanded Custom1" = Table.ExpandRecordColumn(#"Expanded Custom", "Custom", {"date", "localName", "name", "countryCode", "fixed", "global", "counties", "launchYear", "types"}, {"date", "localName", "name", "countryCode", "fixed", "global", "counties", "launchYear", "types"}),
    #"Expanded counties" = Table.ExpandListColumn(#"Expanded Custom1", "counties"),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded counties",{"fixed", "localName", "types", "launchYear"})
in
    #"Removed Columns"

I create a table with just the years 2020 through to 2024 and use this base column year number as part of the url for an API call, so it is dynamic. Unfortunately when I try to create this as a dataflow in the Service and paste the above code in, when saving, things seem to compile until the very end when I get a pop up error saying 'Can't save dataflow. One or more tables references a dynamic data source'.

What am I doing wrong and how can I fix this to allow this to run in the Service?