Testflight: Build is not in an internally testable state

Hello,

I am trying to add a build from xcode cloud to a Testflight internal testing group but I get the following error:

{
  "errors" : [ {
    "id" : "a1bf6ab5-de5e-47bf-b5e8-232baf70ab97",
    "status" : "422",
    "code" : "ENTITY_UNPROCESSABLE",
    "title" : "Build is not assignable.",
    "detail" : "Build is not in an internally testable state."
  } ]
}

I have to mention that before yesterday (6th of March 2023) I had no issues with Testflight. Nothing changed in my project configuration, just some UI changes.

I would appreciate any help I can get.

Thank you in advance for your help.