There are several threads about that already. No need to start another one.
It’s seems MS/Asobo’s servers aren’t the problem in most cases. The problem can occur currently for both MSFS2020 and MSFS2024
In case you are from Germany: this might help. In case you aren’t from Germany it might still help. This can happen with any internet service provider.
There the problem lies with the DNS servers. Download speed tests are perfect, nevertheless MSFS2024 runs very badly. With different DNS servers set (manual how to do that is in the thread) you could be set.