Hello, you linked the wrong document (that one is to do with individual player registration) and the one you are looking for can be found here at the bottom titled "Regulamento Específico da Competição - Série A do Campeonato Brasileiro 2023":
https://www.cbf.com.br/futebol-brasileiro/noticias/campeonato-brasileiro-serie-a/conselho-tecnico-aprova-novidades-no-brasileirao-2023.
The rules state:
"Chapter 3, Art.9, point 1 - "Clubs will be able to register a maximum number of 50 (fifty) athletes until 08/25/2023, and may replace a maximum of 8 (eight) athletes until 09/15/2023, among those previously registered."
Players complaining about not being registered is a normal gameplay response. If you can only make 8 squad selection changes then you should not be signing more than 8 players that you intend to register and it would be a fair reaction for players that would expect to be registered to complain about not being registered. It works the same way when players are left off of continental registration lists.
For this example, we need to investigate how you already managed to max out the 8 squad selection changes and this is why we need a save game file from before the start of the registration period in order to investigate further.