After trying the tips that @jsmyth sent me, CheckMK was able to synchronize just one user (because I create a filter just with my uid, for testing purposes), but when I try to login with my user using LDAP credentials the login fails.
Checking the logs in var/log/web.log I found this:
2022-09-22 19:10:23,280 [30] [cmk.web.auth 1401718] Login failed for username: myusername
For me looks like the CheckMK is not using LDAP to log in to users, exists any way to check why this is happening?