Players time out while logging in
What it looks like in your log
Took too long to log in
What causes it
Joins exceed the login window. On big modpacks that is slow clients syncing data; on vanilla it usually means the server itself is stalling.
How to fix it
On Forge, raise the connection timeout in the server config. On Paper or vanilla, look at server lag first; login timeouts are usually a symptom of a stalled tick loop.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log