There is an automated message from aMember Pro script. 
An account violation has been detected for the following
customer:
  User details:
    Username:   {$user.login}
    Email:      {$user.email}
    Name:       {$user.name_f} {$user.name_l}
{if $config.max_ip_actions ne "2"}
Customer account has been automatically locked.
{/if}
    
It has reached configured limit of {$config.max_ip_count} IP within
{$config.max_ip_period} hours. Please login into aMember CP and review
his access log. 

If it looks like a script mistake, you may disable sharing violation checking 
for this user in the "User Profile", or disable it globally at aMember CP -> 
Setup -> Advanced by setting "Max Number of IP" to something like "99999".
    
--
Your aMember Pro script 
{$config.root_url}/admin/