I think that this suggests that a network issue might be causing the connection to close prematurely.
I suggest examining your network connection, especially things like proxies, firewalls, VPNs, regional internet-block issues, etc. You might want to experiment with using different a network connection via VPN or mobile hotspot, or try using a different network connection altogether if your computer is mobile.
Workarounds:
- Install Anki 25.02.7. That is an older version, the last before the switch to the new installer.
- Possibly consider installing All in Anki. Warning: this is not an official Anki package. Instead, a community member pre-built Anki into an all-in-one package that doesn’t require further installation steps. But, it is not official, and you would need to decide whether you trust the person who made it.