All of our licenses are limited to one domain and when a user active his license for first time and then remove license option ( by removing database for example ), by re-entering license for reactivation this error will be displayed although domain name is not changed :

Reached maximum allowable domains.

In activation_api_listener function that located on /includes/slm-api-listener.php file the plugin first check if maximum allowed domain is reached or not but it’s better to compare requested domain by registered domain and if this two variables are not equal then check domain activation limit.