doveadm(root): Error: Couldn't drop privileges: User is missing UID

hi, I have a server for a long time with the latest version of ispconfig that works as a mail archive and has always worked correctly, now a problem has appeared; doing text searches on the roundcube webmail not all results are found (Solr is installed to speed up searches) So I tried to regenerate the index with doveadm (it worked in the past) but I get this error:

Code:

# doveadm -v index [email protected]
doveadm(root): Error: Couldn't drop privileges: User is missing UID (see mail_uid setting)

# doveadm -v index '*'
doveadm(root): Error: Couldn't drop privileges: User is missing UID (see mail_uid setting)

I have been beating my head with tests and researches online for days but I can't solve the problem, this is the dovecot configuration:

Code:

# dovecot -n
# 2.3.7.2 (3c910f64b): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.7.2 ()
# OS: Linux 5.4.0-121-generic x86_64 Ubuntu 20.04.4 LTS
# Hostname: archive.bbbbb.com
auth_master_user_separator = *
auth_mechanisms = plain login
default_vsz_limit = 1500 M
disable_plaintext_auth = no
listen = *,[::]
lmtp_rcpt_check_quota = yes
log_timestamp = "%Y-%m-%d %H:%M:%S "
mail_max_userip_connections = 100
mail_plugins = " quota acl fts fts_solr"
mail_privileged_group = vmail
passdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}
passdb {
  args = /etc/dovecot/passwd.masterusers
  driver = passwd-file
  master = yes
  result_success = continue
}
passdb {
  driver = shadow
}
plugin {
  acl = vfile:/etc/dovecot/dovecot-acl
  fts = solr
  fts_autoindex = yes
  fts_solr = url=http://54.37.100.20:8983/solr/dovecot/
  quota = dict:user::file:/var/vmail/%d/%n/.quotausage
  quota_status_nouser = DUNNO
  quota_status_overquota = 552 5.2.2 Mailbox is full
  quota_status_success = DUNNO
  sieve = /var/vmail/%d/%n/.sieve
  sieve_after = /var/vmail/%d/%n/.ispconfig.sieve
  sieve_before = /var/vmail/%d/%n/.ispconfig-before.sieve
  sieve_max_actions = 100
  sieve_max_redirects = 25
  sieve_max_script_size = 2M
}
postmaster_address = [email protected]
protocols = imap pop3
service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = postfix
    mode = 0660
    user = postfix
  }
  unix_listener auth-userdb {
    group = vmail
    mode = 0600
    user = vmail
  }
  user = root
}
service imap-login {
  client_limit = 1000
  process_limit = 512
}
service lmtp {
  unix_listener /var/spool/postfix/private/dovecot-lmtp {
    group = postfix
    mode = 0600
    user = postfix
  }
}
service quota-status {
  client_limit = 1
  executable = quota-status -p postfix
  unix_listener /var/spool/postfix/private/quota-status {
    group = postfix
    mode = 0660
    user = postfix
  }
}
service stats {
  unix_listener stats-reader {
    group = vmail
    mode = 0660
    user = vmail
  }
  unix_listener stats-writer {
    group = vmail
    mode = 0660
    user = vmail
  }
}
ssl_cert = </etc/postfix/smtpd.cert
ssl_cipher_list = ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384
ssl_dh = # hidden, use -P to show it
ssl_key = # hidden, use -P to show it
ssl_min_protocol = TLSv1.2
userdb {
  driver = prefetch
}
userdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}
userdb {
  driver = passwd
}
protocol imap {
  auth_verbose = yes
  default_vsz_limit = 1500 M
  mail_plugins = " quota acl fts fts_solr imap_acl quota imap_quota"
}
protocol pop3 {
  auth_verbose = yes
  mail_plugins = quota
  pop3_uidl_format = %08Xu%08Xv
}
protocol lda {
  mail_plugins = sieve quota
  postmaster_address = [email protected]
}
protocol lmtp {
  mail_plugins = quota sieve
  postmaster_address = [email protected]
}

some idea? Thanks in advance