Hi,
The issue with error codes 91 and 93 usually isn't a Windows fault but rather bugs within Fortnite itself; an update in 2025 caused this problem for many users.
Some players managed to fix it by using Creative mode to join a party, then leaving and switching to Battle Royale mode.
In some cases, it was an account-related issue, so try testing with a different account and set your lobby to "Public" to see if that works.
Thanks.